JP2022544637A - Spatially multiplexed volume Bragg gratings with various refractive index modulations for waveguide displays - Google Patents

Abstract

The waveguide display comprises a waveguide that transmits visible light, a first volume Bragg grating (VBG) on the waveguide and characterized by a first refractive index modulation, a first volume Bragg grating (VBG) on the waveguide and a different and a second reflective VBG comprising a plurality of regions characterized by a refractive index modulation of . The first reflective VBG is configured to diffract display light in a first wavelength range and a first field of view (FOV) range, resulting in the first wavelength range and first FOV range. The display light propagates within the waveguide through total internal reflection to multiple regions of the second reflected VBG. The plurality of regions of the second reflective VBG are configured to diffract display light in different respective wavelength ranges within the first wavelength range and the first FOV range. [Selection drawing] Fig. 36

Description

The present invention relates generally to volume Bragg grating-based waveguide displays for near-eye displays.

Artificial reality systems, such as head-mounted display (HMD) or head-up display (HUD) systems, typically present content to users via electronic or optical displays within about 10-20 mm in front of the user, for example. including near-eye displays (eg, in the form of headsets or eyeglasses) configured to Near-eye displays can display virtual objects or combine images of real objects with virtual objects, such as in virtual reality (VR), augmented reality (AR), or mixed reality (MR) applications. For example, in AR systems, a user sees images of both virtual objects (e.g., computer-generated images (CGI)) and the surrounding environment, e.g., by looking through transparent display glasses or lenses (often referred to as optical see-through). can see.

An example of an optical see-through AR system may use a waveguide-based optical display, where the light of the projected image is coupled into a waveguide (e.g., a transparent substrate), propagates within the waveguide, and has different It can be coupled out from the waveguide at a location. In some implementations, the light of the projected image can be coupled into or out of the waveguide using a diffractive optical element such as a grating. Light from the ambient environment can pass through the see-through region of the waveguide and reach the user's eyes as well.

The present invention relates generally to volume Bragg grating-based waveguide displays for near-eye displays. More specifically, it is disclosed herein to extend the eyebox, reduce display haze, reduce physical size, improve optical efficiency, reduce optical artifacts. , and techniques for increasing the field of view of optical see-through near-eye display systems using volume Bragg grating (VBG) couplers. Various inventive embodiments are described herein including devices, systems, methods, and so on.

In one aspect, the present invention provides a substrate, a first reflective VBG, on the substrate, and characterized by a first refractive index modulation, on the substrate, and the first and second regions. and a second reflective VBG. The first reflective VBG is configured to diffract the display light in the first wavelength range such that the display light in the first wavelength range passes through the substrate through total internal reflection to the second propagates to the first and second regions of the reflected VBG. The first region of the second reflected VBG may be characterized by a second refractive index modulation that is lower than the first refractive index modulation, and display light in a second wavelength range that is within the first wavelength range. can be configured to diffract the A second region of the second reflective VBG may be characterized by a third refractive index modulation that is greater than the second refractive index modulation and includes a second wavelength range and a third wavelength that is greater than the second wavelength range. It can be configured to diffract display light in a range. The first and second regions of the second reflected VBG may be arranged such that display light in the first wavelength range reaches the second region after reaching the first region.

In some embodiments, the first reflected VBG and the second reflected VBG may have the same grating vector in the plane perpendicular to the surface normal direction of the substrate. The third refractive index modulation may be equal to or less than the first refractive index modulation, and the first wavelength range may be the same as or include the third wavelength range. In some embodiments, the second reflective VBG may further include a third region between the first region and the second region, the third region having a higher refractive index than the second refractive index modulation. displaying light in a fourth wavelength range that includes the second wavelength range and is within the third wavelength range, characterized by a fourth refractive index modulation that is greater but less than the third refractive index modulation; It can be configured to diffract.

In some embodiments, the waveguide display is multiplexed with a first reflective VBG, a third reflective VBG characterized by a fourth refractive index modulation, and a It may further include a fourth reflection VBG multiplexed with the second reflection VBG. The third reflective VBG is configured to diffract the display light in the fourth wavelength range such that the display light in the fourth wavelength range passes through the substrate through total internal reflection to the fourth wavelength. propagates to the first and second regions of the reflected VBG. The first region of the fourth reflective VBG may be characterized by a fifth refractive index modulation lower than the fourth refractive index modulation, the display light being in a fifth wavelength range within the fourth wavelength range. can be configured to diffract the A second region of the fourth reflective VBG may be characterized by a sixth refractive index modulation greater than the fifth refractive index modulation, including a fifth wavelength range and a sixth wavelength greater than the fifth wavelength range. It can be configured to diffract display light in a range.

In some embodiments, the first reflected VBG diffracts display light in a first wavelength range and a first field of view (FOV) range, and a fourth wavelength range and a first FOV range. It can be configured to diffract display light in a different second FOV range. In some embodiments, the substrate may be transparent to visible light and the second reflective VBG may be transparent to visible light from the surrounding environment. In some embodiments, the first reflected VBG may be configured to couple display light in the first wavelength range into the substrate, and the second reflected VBG is in the first wavelength range. It may be configured to couple display light from the substrate. In some embodiments, the waveguide display may further include a third grating and a fourth grating, the third grating directing display light in the first wavelength range from the first reflected VBG to a third grating. The fourth grating may be configured to diffract to four gratings, the fourth grating configured to diffract display light in the first wavelength range in the two or more regions of the fourth grating to the second reflected VBG. can be The third grating and the fourth grating may have the same grating vector in a plane perpendicular to the surface normal direction of the substrate.

In some embodiments, the waveguide display includes an input coupler configured to couple display light in a first wavelength range into the substrate and display light diffracted by a second reflected VBG into the substrate. and an output coupler configured to couple out from. The input and output couplers may contain multiplexed VBGs. In some embodiments, the waveguide display includes a light source configured to generate display light, and projector optics configured to collimate the display light and direct the display light toward the first reflected VBG. can further include

In another aspect, the invention provides a waveguide transparent to visible light, a first VBG on the waveguide and characterized by a first refractive index modulation, and a different respective VBG on the waveguide and on the waveguide. A waveguide display is provided that may include a second reflective VBG that includes a plurality of regions characterized by refractive index modulation. The first reflective VBG may be configured to diffract display light in the first wavelength range and the first FOV range, resulting in display light in the first wavelength range and the first FOV range. may propagate in the waveguide through total internal reflection to regions of the second reflected VBG. The plurality of regions of the second reflective VBG may be configured to diffract display light in different respective wavelength ranges within the first wavelength range and the first FOV range. The first reflection VBG and the second reflection VBG may have the same grating vector in the plane perpendicular to the plane normal direction of the waveguide.

In some embodiments of the waveguide display, at least one of the first refractive index modulation and different respective refractive index modulations of the plurality of regions of the second reflective VBG is a minimum for diffraction efficiency saturation. It may be larger than the refractive index modulation. In some embodiments, the plurality of regions of the second reflective VBG is such that the display light in the first wavelength range and the first FOV range is the first of the plurality of regions having the second refractive index modulation. After reaching the region, it may be configured to reach a second region of the plurality of regions having a third refractive index modulation greater than the second refractive index modulation.

In some embodiments, the first reflected VBG can be configured to couple display light in the first wavelength range and the first FOV range into the waveguide, and the second reflected VBG can: It may be configured to couple out display light in a first wavelength range and a first FOV range from the waveguide, and may transmit visible light from the ambient environment. In some embodiments, the waveguide display can also include a third grating and a fourth grating. A third grating may be configured to diffract display light in the first wavelength range and the first FOV range from the first reflective grating to the fourth grating. A fourth grating may be configured to diffract display light in the first wavelength range and the first FOV range in two or more regions of the fourth grating to the second reflected VBG. The third grating and the fourth grating may have the same grating vector in the plane perpendicular to the plane normal direction of the waveguide.

The invention is defined in the appended claims. This Summary of the Invention is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation to determine the scope of the claimed subject matter not. The subject matter is to be understood by reference to appropriate portions of the entire specification, any or all drawings, and claims of the present disclosure. The foregoing, along with other features and examples, are explained in more detail below in the specification, claims, and accompanying drawings that follow. It is to be understood that any feature discussed as suitable for inclusion in any of the aspects described herein is also suitable for inclusion in any of the other aspects, in any combination.

Illustrative embodiments are described in detail below with reference to the following figures.

1 is a simplified block diagram of an example artificial reality system environment including a near-eye display system, in accordance with certain embodiments; FIG. 1 is a perspective view of an example near-eye display system in the form of a head-mounted display (HMD) device for implementing some of the examples disclosed herein; FIG. 1 is a perspective view of an example near-eye display system in the form of eyeglasses for implementing some of the examples disclosed herein; FIG. 1 is a simplified diagram illustrating an example of an optical system within a near-eye display system; FIG. FIG. 10 illustrates an example optical see-through augmented reality system including a waveguide display for exit pupil expansion, in accordance with certain embodiments. FIG. 10 illustrates an example optical see-through augmented reality system including a waveguide display for exit pupil expansion, in accordance with certain embodiments. FIG. 2 illustrates the spectral bandwidth of an example reflective volume Bragg grating (VBG) and the spectral bandwidth of an example transmissive surface relief grating (SRG); FIG. 2 illustrates the angular bandwidth of an example reflective VBG and the angular bandwidth of an example transmissive SRG; FIG. 15 illustrates an example optical see-through augmented reality system including a waveguide display and surface relief grating for exit pupil expansion, in accordance with certain embodiments. FIG. 10 illustrates an example eyebox that includes a two-dimensional replicated exit pupil, in accordance with certain embodiments; FIG. 4 illustrates the wavevector of light diffracted by an example surface relief grating for exit pupil enlargement in a waveguide display and the exit pupil for multiple colors; FIG. 10 illustrates field clipping with an example surface relief grating for exit pupil enlargement in a waveguide display. 4A-4C illustrate examples of volume Bragg grating-based waveguide displays, in accordance with certain embodiments. 10B is a top view of the example volume Bragg grating-based waveguide display shown in FIG. 10A. FIG. 10B is a side view of the example volume Bragg grating-based waveguide display shown in FIG. 10A. FIG. FIG. 4 illustrates optical dispersion in an example volume Bragg grating-based waveguide display, in accordance with certain embodiments. 1 illustrates an example of a volume Bragg grating (VBG); FIG. 12B illustrates the Bragg condition for the volume Bragg grating shown in FIG. 12A; FIG. 1 is a front view of an example volume Bragg grating-based waveguide display with exit pupil enlargement and dispersion reduction, in accordance with certain embodiments; FIG. 13B is a side view of the example volume Bragg grating-based waveguide display shown in FIG. 13A. FIG. FIG. 2 illustrates the propagation of light from different fields of view in a reflective volume Bragg grating-based waveguide display, in accordance with certain embodiments. FIG. 2 illustrates the propagation of light from different fields of view in a transmissive volume Bragg grating-based waveguide display, in accordance with certain embodiments; FIG. 2 illustrates an example of a reflective volume Bragg grating-based waveguide display with exit pupil expansion and dispersion reduction, in accordance with certain embodiments. FIG. 2 illustrates an example of a transmissive volume Bragg grating-based waveguide display with exit pupil expansion and form factor reduction, in accordance with certain embodiments. 4A-4C illustrate examples of transmissive volume Bragg gratings in waveguide displays, in accordance with certain embodiments. FIG. 4 illustrates an example of a transmissive VBG in a waveguide display, where light diffracted by a reflective VBG is not fully reflected and directed within the waveguide; 4A-4C illustrate examples of reflective volume Bragg gratings in waveguide displays, in accordance with certain embodiments. FIG. 4 illustrates an example of a reflected VBG in a waveguide display, where light diffracted by a transmitted VBG is not fully reflected and directed within the waveguide; FIG. 10 illustrates light dispersion by an example of a reflective volume Bragg grating in a waveguide display, in accordance with certain embodiments. FIG. 10 illustrates optical dispersion by an example transmissive volume Bragg grating in a waveguide display, in accordance with certain embodiments. 1 is a front view of an example volume Bragg grating-based waveguide display with exit pupil enlargement and dispersion reduction, in accordance with certain embodiments; FIG. 1 is a side view of an example volume Bragg grating-based waveguide display including an image projector and multiple polymer layers, in accordance with certain embodiments. FIG. FIG. 12 illustrates another example volume Bragg grating-based waveguide display with exit pupil enlargement, dispersion reduction, form factor reduction, and power efficiency improvement, in accordance with certain embodiments. 20B illustrates an example of a replicated exit pupil in the eyebox of the volume Bragg grating-based waveguide display shown in FIG. 20A; FIG. FIG. 15 illustrates an example volume Bragg grating-based waveguide display with exit pupil enlargement, dispersion reduction, and form factor reduction, in accordance with certain embodiments. FIG. 10 illustrates an example volume Bragg grating-based waveguide display with exit pupil enlargement, dispersion reduction, form factor reduction, and efficiency improvement, in accordance with certain embodiments. 1 is a front view of an example volume Bragg grating-based waveguide display including two image projectors, in accordance with certain embodiments; FIG. FIG. 4 is a side view of an example volume Bragg grating-based waveguide display including two image projectors, in accordance with certain embodiments. 1 is a front view of an example volume Bragg grating-based waveguide display including a single image projector and a grating for field stitching, in accordance with certain embodiments; FIG. FIG. 4 is a side view of an example volume Bragg grating-based waveguide display with a single image projector and a grating for field stitching, in accordance with certain embodiments. FIG. 10 illustrates an example volume Bragg grating-based waveguide display including multiple grating layers for different fields of view and/or light wavelengths, in accordance with certain embodiments. FIG. 10 illustrates the fields of view of multiple gratings in an example volume Bragg grating-based waveguide display, in accordance with certain embodiments. FIG. 2 illustrates the diffraction of different colors of light from different corresponding fields of view by the example of a volume Bragg grating; FIG. 2 illustrates the relationship between the grating period of a volume Bragg grating and the corresponding fields of view for different colors of incident light. FIG. 4 illustrates the diffraction efficiency of an example transmissive volume Bragg grating with the same thickness but different refractive index modulation; FIG. 4 illustrates the diffraction efficiency of an example reflective volume Bragg grating with the same thickness but different refractive index modulations. FIG. 4 illustrates the diffraction efficiency of an example transmission volume Bragg grating with a first refractive index modulation as a function of the angle of incidence deviation from the Bragg condition; FIG. 4 illustrates the diffraction efficiency of an example transmission volume Bragg grating with a second refractive index modulation as a function of the angle of incidence deviation from the Bragg condition; FIG. 4 illustrates the diffraction efficiency of an example transmission volume Bragg grating with a third refractive index modulation as a function of the angle of incidence deviation from the Bragg condition; FIG. 4 illustrates the diffraction efficiency of an example transmission volume Bragg grating with a fourth refractive index modulation as a function of the angle of incidence deviation from the Bragg condition; FIG. 4 illustrates the diffraction efficiency of an example reflective volume Bragg grating with a first refractive index modulation as a function of the angle of incidence deviation from the Bragg condition; FIG. 5 illustrates the diffraction efficiency of an example reflective volume Bragg grating with a second refractive index modulation as a function of the angle of incidence deviation from the Bragg condition; FIG. 4 illustrates the diffraction efficiency of an example reflective volume Bragg grating with a third refractive index modulation as a function of the angle of incidence deviation from the Bragg condition; FIG. 4 illustrates the diffraction efficiency of an example reflective volume Bragg grating with a fourth refractive index modulation as a function of the angle of incidence deviation from the Bragg condition; FIG. 2 illustrates the diffraction efficiency of an example transmissive VBG with a first refractive index modulation for blue light from different fields of view; FIG. 10 illustrates the diffraction efficiency of an example transmissive VBG with a first refractive index modulation for green light from different fields of view; FIG. 10 illustrates the diffraction efficiency of an example transmissive VBG with a first refractive index modulation for red light from different fields of view; FIG. 10 illustrates the diffraction efficiency of an example transmissive VBG with a second refractive index modulation for blue light from different fields of view; FIG. 10 illustrates the diffraction efficiency of an example transmissive VBG with a second refractive index modulation for green light from different fields of view; FIG. 10 illustrates the diffraction efficiency of an example transmissive VBG with a second refractive index modulation for red light from different fields of view; FIG. 10 illustrates the diffraction efficiency of an example transmissive VBG with a third refractive index modulation for blue light from different fields of view; FIG. 10 illustrates the diffraction efficiency of an example transmissive VBG with a third refractive index modulation for green light from different fields of view; FIG. 10 illustrates the diffraction efficiency of an example transmissive VBG with a third refractive index modulation for red light from different fields of view; FIG. 2 illustrates the minimum refractive index modulation of transmissive volume Bragg gratings with different grating periods to achieve diffraction saturation for different colors of light. FIG. 5 shows maximum refractive index modulation for transmission gratings with different grating periods to avoid refractive index modulation saturation for blue, green, and red light; FIG. 10 illustrates an example grating layer including multiplexed VBGs of different pitch and refractive index modulations for optimized diffraction efficiency and uniformity, in accordance with certain embodiments. FIG. 4 illustrates FOV crosstalk induced by an example of a multiplexed volume Bragg grating; FIG. 2 illustrates the relationship between the grating period of a volume Bragg grating and the corresponding fields of view for different colors of incident light. FIG. 5 illustrates linewidths of Bragg peaks of transmission and reflection volume Bragg gratings for different fields of view; FIG. 2 illustrates examples of Bragg peaks of transmission volume Bragg gratings for different fields of view; FIG. 2 illustrates examples of Bragg peaks of a reflective volume Bragg grating for different fields of view; FIG. 4 illustrates the trade-off between crosstalk and efficiency in an example multiplexed volume Bragg grating; FIG. 4 illustrates the trade-off between crosstalk and efficiency in an example multiplexed volume Bragg grating; FIG. 4 illustrates the relationship between minimum diffraction efficiency and total refractive index modulation and corresponding crosstalk in a multiplexed transmission volume Bragg grating; FIG. 4 illustrates the relationship between minimum diffraction efficiency and total refractive index modulation and corresponding crosstalk in a multiplexed reflective volume Bragg grating. 4A-4C illustrate examples of waveguide displays including spatially multiplexed reflective volume Bragg gratings with different refractive index modulations, in accordance with certain embodiments. FIG. 2 illustrates an example waveguide display including two multiplexed volume Bragg gratings and a polarization converter between the two multiplexed volume Bragg gratings, in accordance with certain embodiments. FIG. 2 illustrates an example waveguide display including an antireflective layer and an angle-selective transmissive layer, in accordance with certain embodiments. 1 is a simplified block diagram of an example electronic system in an example near-eye display, in accordance with certain embodiments; FIG.

The figures depict embodiments of the present invention for purposes of illustration only. Those skilled in the art will appreciate from the following description that alternate embodiments of the structures and methods illustrated can be employed without departing from the principles or claimed benefits of the present invention.

In the accompanying figures, similar components and/or features may have the same reference label. Additionally, various components of the same type may be distinguished by following the reference label with a dash and by a second label that distinguishes between similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label regardless of the second reference label. is.

The present invention relates generally to volume Bragg grating (VBG)-based waveguide displays for near-eye display systems. In near-eye display systems, generally enlarging the eyebox, reducing display haze, improving image quality (e.g., resolution and contrast), reducing physical size, and increasing power efficiency and to increase the field of view. In a waveguide-based near-eye display system, the light of the projected image is coupled into a waveguide (e.g., a transparent substrate), propagates within the waveguide, and diverges to replicate the exit pupil and enlarge the eyebox. It can be coupled out from the waveguide at a location. More than one grating can be used to expand the exit pupil in two dimensions. In waveguide-based near-eye display systems for augmented reality applications, light from the surrounding environment can pass through at least the see-through region (eg, transparent substrate) of the waveguide display and reach the user's eyes. In some implementations, the light of the projected image can be coupled into or out of the waveguide using a diffractive optical element such as a grating.

Optical couplers implemented using diffractive optical elements may have a limited field of view due to the angular dependence of grating efficiency. Therefore, light incident on the coupler from multiple angles of incidence (eg, from different fields of view) may not be diffracted with equal or similar efficiency. In addition, couplers implemented using diffractive optical elements may cause dispersion between different colors of light, and different colors of light may have different diffraction angles. Therefore, different light components in a color image may not overlap each other. Hence, the quality of the displayed image (eg, color reproduction neutrality) may be reduced. Furthermore, the field of view for light of different colors may be reduced or partially clipped due to the limited range of light dispersion and wavevectors of light that can be guided by waveguide displays. . To reduce dispersion and improve field-of-view (FOV) range and diffraction efficiency, thick transmissive and/or reflective VBG gratings containing many multiplexed gratings are used to cover different fields of view for different color components. In many cases, this can be impractical and/or can cause significant display and see-through haze due to the thickness of the grating and the large amount of exposure for recording multiplexed VBG gratings. For example, in some cases a transmission VBG grating with a thickness greater than 1 mm may be required to reduce dispersion and achieve the desired FOV range and diffraction efficiency. A reflective VBG grating with a relatively smaller thickness may be used to achieve the desired performance. However, with reflective gratings, the gratings for two-dimensional pupil expansion may not overlap, so the physical size of the waveguide display can be large and the display haze can still be significant.

According to certain embodiments, two VBG gratings (or two portions of the same grating) with matching grating vectors (e.g., having the same grating vector in the plane perpendicular to the surface normal direction of the transparent substrate) are displayed. It can be used to diffract light and enlarge the exit pupil in one dimension. The two VBG gratings can compensate for the dispersion of the display light caused by each other and reduce the overall dispersion due to the opposite Bragg conditions (eg, +1st and −1st orders of diffraction) in the two VBG gratings. . Therefore, a thin VBG grating can be used and still achieve the desired resolution. Because of dispersion compensation, a thin transmissive VBG grating can be used to achieve the desired resolution, and a grating for two-dimensional pupil expansion is at least partially used to reduce the physical size of the waveguide display. can be duplicated.

In some embodiments, to achieve the desired FOV, coupling efficiency, and coupling efficiency uniformity across the entire FOV and color spectrum, multiple VBG layers including multiplexed VBGs are integrated into one or more waveguides. It can be formed into a plate. Each VBG layer can be used to couple light within a particular FOV and/or color range with relatively high efficiency, and a combination of multiple VBG layers is desired with relatively high and uniform coupling efficiency. of FOV and full coverage of color gamut.

In some embodiments, a first pair of VBG gratings (or two portions of gratings) can be used to expand the exit pupil in one dimension and compensate for dispersion caused by each other; A pair of VBG gratings (or two portions of the gratings) can be used to expand the exit pupil in another dimension and compensate for the dispersion caused by each other. Hence, the exit pupil can be replicated in two dimensions and the resolution of the displayed image can be increased in both dimensions.

According to certain embodiments, the first pair and/or the second pair of gratings may each include multiplexed reflective volume Bragg gratings. A multiple reflection VBG may include reflection VBGs that may have high diffraction efficiency and low crosstalk between reflection VBGs within the multiple reflection VBG. In some embodiments, the reflective VBG may have a refractive index modulation greater than the minimum refractive index modulation for diffraction efficiency saturation, thus resulting in high diffraction efficiency and a wide half-width-half-maximum (FWHM) wavelength range and/or It can have a FWHM angle range. As such, a less reflective VBG can be used to cover the wavelength range and full FOV of the light source to improve the efficiency and performance of the waveguide display.

In some embodiments, each of the first pair of gratings and/or the second pair of gratings has a first reflective VBG characterized by a first refractive index modulation and a different respective refractive index modulation. A second reflective VBG may be included that includes multiple regions to be characterized. The first reflective VBG may be configured to diffract display light in a first wavelength range (and/or first FOV range) such that the first wavelength range (and/or first FOV range) Display light in the FOV range of ) can propagate in the waveguide through total internal reflection to multiple regions of the second reflected VBG. The plurality of regions of the second reflected VBG have different respective wavelength (and/or FOV) ranges within the first wavelength range (and/or first FOV range) due to different respective refractive index modulations. can be configured to diffract the display light at The first reflection VBG and the second reflection VBG may have the same grating vector in the plane perpendicular to the plane normal direction of the waveguide to reduce dispersion. At least one of the first refractive index modulation and the different respective refractive index modulations of the plurality of regions of the second reflective VBG may be greater than the minimum refractive index modulation for diffraction efficiency saturation. Regions of the second reflected VBG are such that display light in the first wavelength range (and/or the first FOV range) reaches the first region with lower refractive index modulation in the plurality of regions Later it can be arranged to reach a second region with a higher refractive index modulation in the plurality of regions. In this manner, display light in a narrower portion of the first wavelength range (and/or first FOV) can be diffracted by the first region, resulting in the first wavelength range (and/or first FOV) ) but outside the narrower portion may be diffracted by the second region.

In the following description, various inventive embodiments including devices, systems, methods, etc. are described. For purposes of explanation, specific details are set forth in order to provide a thorough understanding of examples of the invention. It is evident, however, that various examples may be practiced without these specific details. For example, devices, systems, structures, assemblies, methods, and other components may be shown as components in block diagram form in order not to obscure the examples in unnecessary detail. . In other instances, well-known devices, processes, systems, structures, and techniques may be shown without necessary detail to avoid obscuring the examples. Illustrations and descriptions are not meant to be limiting. The terms and expressions employed in this disclosure are used as terms of description rather than of limitation, and use of such terms and expressions excludes any equivalents or portions thereof of the features shown and described. No intention. The word "example" is used herein to mean "serving as an example, instance, or illustration." Any embodiment or design described herein as an "example" is not necessarily to be construed as preferred or advantageous over other embodiments or designs.

FIG. 1 is a simplified block diagram of an example artificial reality system environment 100 including a near-eye display 120, in accordance with certain embodiments. Artificial reality system environment 100 shown in FIG. can be Although FIG. 1 shows an example artificial reality system environment 100 including one near-eye display 120, one external imaging device 150, and one input/output interface 140, any number of these components may be artificial. It may be included in the real system environment 100, or any of the components may be omitted. For example, there may be multiple near-eye displays 120 monitored by one or more external imaging devices 150 in communication with console 110 . In some configurations, artificial reality system environment 100 may not include external imaging device 150 , optional input/output interface 140 , and optional console 110 . Different or additional components may be included in the artificial reality system environment 100 in alternative configurations.

Near-eye display 120 may be a head-mounted display that presents content to the user. Examples of content presented by near-eye display 120 include one or more of images, video, audio, or any combination thereof. In some embodiments, audio is provided by an external device (e.g., speakers and/or headphones) that receives audio information from near-eye display 120, console 110, or both, and presents audio data based on this audio information. can be presented via Near-eye display 120 may include one or more rigid bodies that may be rigidly or non-rigidly coupled to each other. A rigid connection between rigid bodies can cause the connected rigid bodies to act as a single rigid body. A non-rigid connection between rigid bodies may allow the rigid bodies to move relative to each other. In various embodiments, near-eye display 120 may be implemented in any suitable form factor, including eyeglasses. Some embodiments of near-eye display 120 are further described below with respect to FIGS. Additionally, in various embodiments, the functionality described herein can be used in headsets that combine images of the environment external to the near-eye display 120 and artificial reality content (eg, computer-generated images). Accordingly, the near-eye display 120 uses the generated content (e.g., images, videos, sounds, etc.) to generate images of the physical real-world environment outside the near-eye display 120 in order to present augmented reality to the user. can be extended.

In various embodiments, near-eye display 120 may include one or more of display electronics 122 , display optics 124 , and eye-tracking unit 130 . In some embodiments, near-eye display 120 may also include one or more locators 126 , one or more position sensors 128 , and inertial measurement unit (IMU) 132 . Near-eye display 120 may omit any of eye-tracking unit 130, locator 126, position sensor 128, and IMU 132, or may include additional elements in various embodiments. Additionally, in some embodiments, near-eye display 120 may include elements that combine the functionality of various elements described in conjunction with FIG.

Display electronics 122 may display images or facilitate the display of images to a user, for example, according to data received from console 110 . In various embodiments, the display electronics 122 include a liquid crystal display (LCD), an organic light emitting diode (OLED) display, an inorganic light emitting diode (ILED) display, a micro light emitting diode (μLED) display, an active matrix OLED display (AMOLED), It may include one or more display panels, such as a transparent OLED display (TOLED), or some other display. For example, in one implementation of the near-eye display 120, the display electronics 122 include a front TOLED panel, a rear display panel, and optical components (e.g., attenuators, polarizers) between the front and rear display panels. , or diffraction or spectral films). Display electronics 122 may include pixels to emit primary colors of light such as red, green, blue, white, or yellow. In some implementations, display electronics 122 may display three-dimensional (3D) images through a stereoscopic effect produced by a two-dimensional panel to create a subjective perception of image depth. For example, display electronics 122 may include left and right displays positioned in front of the user's left and right eyes, respectively. The left and right displays may present copies of the image that are horizontally shifted relative to each other to create a stereoscopic effect (eg, perception of image depth by a user viewing the image).

In certain embodiments, display optics 124 optically display image content (eg, using optical waveguides and couplers) or magnify image light received from display electronics 122 to provide an image Optical errors associated with the light may be corrected and the corrected image light may be presented to the user of near-eye display 120 . In various embodiments, display optics 124 affect image light emitted from display electronics 122, for example, substrates, optical waveguides, apertures, Fresnel lenses, convex lenses, concave lenses, filters, input/output couplers, or display electronics 122. It may include one or more optical elements, such as any other suitable optical element available. Display optics 124 may include a combination of different optical elements and mechanical couplings to maintain the relative spacing and orientation of the combined optical elements. One or more optical elements in display optics 124 may have optical coatings such as antireflective coatings, reflective coatings, filtering coatings, or combinations of different optical coatings.

Magnification of image light by display optics 124 may allow display electronics 122 to be physically smaller, lighter in weight, and to consume less power than larger displays. Additionally, magnification may increase the field of view of the displayed content. The amount of magnification of image light by display optics 124 can be changed by adjusting, adding, or removing optical elements from display optics 124 . In some embodiments, display optics 124 may project a displayed image onto one or more image planes that may be further from the user's eyes than near-eye display 120 .

Display optics 124 may also be designed to correct for one or more types of optical errors, such as two-dimensional optical errors, three-dimensional optical errors, or any combination thereof. Two-dimensional errors can include optical aberrations that occur in two dimensions. Exemplary types of two-dimensional errors may include barrel distortion, pincushion distortion, axial chromatic aberration, and lateral chromatic aberration. Three-dimensional errors may include optical errors that occur in three dimensions. Example types of three-dimensional errors may include spherical aberration, coma, field curvature, and astigmatism.

Locators 126 may be objects located at specific locations on near-eye display 120 relative to each other and to a reference point on near-eye display 120 . In some implementations, console 110 may identify locator 126 within images captured by external imaging device 150 to determine the position, orientation, or both of the artificial reality headset. Locators 126 may be LEDs, corner cube reflectors, reflective markers, a type of light source that contrasts with the environment in which near-eye display 120 operates, or any combination thereof. In embodiments where locator 126 is an active component (eg, an LED or other type of light-emitting device), locator 126 may be in the visible band (eg, about 380 nm-750 nm), the infrared (IR) band (eg, about 750 nm). ~1 mm), the ultraviolet band (eg, from about 10 nm to about 380 nm), another portion of the electromagnetic spectrum, or any combination of portions of the electromagnetic spectrum.

External imaging device 150 may be one or more cameras, one or more video cameras, any other device capable of capturing images including one or more of locators 126, or any of them. It can include combinations. Additionally, the external imaging device 150 may include one or more filters (eg, to increase signal-to-noise ratio). External imaging device 150 may be configured to detect light emitted or reflected from locator 126 within the field of view of external imaging device 150 . In embodiments where locators 126 are passive elements (e.g., retroreflectors), external imaging device 150 may include a light source that illuminates some or all of locators 126, which locators 126 are external imaging devices. Light may be retroreflected to the light source within 150 . Low speed calibration data may be communicated from the external imaging device 150 to the console 110, which determines one or more imaging parameters (eg, focal length, focus, frame rate, sensor temperature, shutter speed, aperture, etc.). One or more calibration parameters may be received from console 110 to adjust .

Position sensor 128 may generate one or more measurement signals in response to movement of near-eye display 120 . Examples of position sensor 128 may include accelerometers, gyroscopes, magnetometers, other motion detection or error correction sensors, or any combination thereof. For example, in some embodiments, position sensor 128 includes multiple accelerometers to measure translational motion (eg, front-back, up-down, or left-right) and rotational motion (eg, pitch, yaw, or roll). It may include multiple gyroscopes for measuring. In some embodiments, various position sensors may be oriented orthogonally to each other.

IMU 132 may be an electronic device that generates fast calibration data based on measurement signals received from one or more of position sensors 128 . Position sensor 128 may be located external to IMU 132, internal to IMU 132, or any combination thereof. Based on one or more measurement signals from one or more position sensors 128 , IMU 132 may generate fast calibration data indicating an estimated position of near-eye display 120 relative to its initial position. For example, IMU 132 integrates measurement signals received from accelerometers over time to estimate a velocity vector, and integrates the velocity vector over time to determine the estimated position of a reference point on near-eye display 120. can. Alternatively, IMU 132 may provide sampled measurement signals to console 110 from which fast calibration data may be determined. A reference point may generally be defined as a point in space, but in various embodiments the reference point may also be defined as a point within near-eye display 120 (eg, the center of IMU 132).

Eye tracking unit 130 may include one or more eye tracking systems. Eye tracking may refer to determining eye position, including eye orientation and location, relative to near-eye display 120 . An eye tracking system may include an imaging system to image one or more eyes, optionally producing light directed to the eye such that light reflected by the eye may be captured by the imaging system. may contain a light emitter. For example, eye tracking unit 130 may include a non-coherent or coherent light source (eg, a laser diode) that emits light in the visible or infrared spectrum, and a camera that captures light reflected by the user's eyes. As another example, eye tracking unit 130 may capture reflected radio waves emitted by a small radar unit. Eye-tracking unit 130 may use low-power light emitters that emit light at frequencies and intensities that do not harm the eye or cause physical discomfort. Eye-tracking unit 130 reduces the overall power consumed by eye-tracking unit 130 (e.g., reduces the power consumed by the light emitters and imaging system included in eye-tracking unit 130) while capturing images captured by eye-tracking unit 130. may be positioned to increase the contrast in the image of the scanned eye. For example, in some implementations, eye tracking unit 130 may consume less than 100 milliwatts of power.

The near-eye display 120 may, for example, determine a user's interpupillary distance (IPD), determine gaze direction, introduce depth cues (e.g., blurred images outside the user's primary line of sight), To gather heuristics about user interaction in VR media (e.g., time spent on any particular target, object, or frame as a function of exposure stimuli), based in part on the orientation of at least one of the user's eyes Eye orientation may be used for some other function, or any combination thereof. Since orientation can be determined for both eyes of the user, eye tracking unit 130 may be able to determine where the user is looking. For example, determining the direction of the user's gaze may include determining a convergence point based on the determined orientations of the user's left and right eyes. The convergence point may be the point where the two foveal axes of the user's eye intersect. The direction of the user's gaze may be the direction of a line passing through the midpoint between the convergence point and the pupil of the user's eye.

Input/output interface 140 may be a device that allows a user to send action requests to console 110 . An action request may be a request to perform a particular action. For example, an action request may be to start or end an application, or to perform a particular action within the application. Input/output interface 140 may include one or more input devices. Exemplary input devices include keyboards, mice, game controllers, gloves, buttons, touch screens, or any other suitable device for receiving action requests and communicating received action requests to console 110. obtain. Action requests received by input/output interface 140 may be communicated to console 110, which may perform actions corresponding to the requested actions. In some embodiments, input/output interface 140 may provide tactile feedback to the user according to instructions received from console 110 . For example, input/output interface 140 may provide tactile feedback when an action request is received or when console 110 has already performed the requested action and communicates instructions to input/output interface 140. . In some embodiments, the external imaging device 150 uses an input/output interface 140, such as a controller (eg, which may include an IR light source) or tracking the location or position of the user's hand to determine user movement. can be used for tracking. In some embodiments, near-eye display 120 uses one or more sensors to track input/output interface 140, such as tracking the location or position of a controller or user's hand to determine user movement. An imaging device may be included.

Console 110 provides content to near-eye display 120 for presentation to a user according to information received from one or more of external imaging device 150, near-eye display 120, and input/output interface 140. obtain. In the example shown in FIG. 1, console 110 may include application store 112 , headset tracking module 114 , artificial reality engine 116 , and eye tracking module 118 . Some embodiments of console 110 may include different or additional modules than those described in conjunction with FIG. The functionality described further below may be distributed among the components of console 110 in different manners than described herein.

In some embodiments, console 110 may include a processor and a non-transitory computer-readable storage medium that stores instructions executable by the processor. A processor may include multiple processing units that execute instructions in parallel. A non-transitory computer-readable storage medium may be any memory, such as a hard disk drive, removable memory, solid state drive (eg, flash memory or dynamic random access memory (DRAM)). In various embodiments, the modules of console 110 described in conjunction with FIG. 1 are instructions in a non-transitory computer-readable storage medium that, when executed by a processor, cause the processor to perform the functions described further below. can be encoded as

Application store 112 may store one or more applications for execution by console 110 . An application may include a group of instructions that, when executed by a processor, generate content for presentation to a user. Content generated by an application may be in response to input received from the user via the user's eye movements or input received from input/output interface 140 . Examples of applications may include gaming applications, conferencing applications, video playback applications, or other suitable applications.

Headset tracking module 114 may use slow calibration information from external imaging device 150 to track near-eye display 120 movement. For example, headset tracking module 114 may use observed locators from the slow calibration information and a model of near-eye display 120 to determine the location of the near-eye display 120 reference point. Headset tracking module 114 may also use position information from the fast calibration information to determine the position of the reference point of near-eye display 120 . Additionally, in some embodiments, headset tracking module 114 uses portions of fast calibration information, slow calibration information, or any combination thereof to predict the future location of near-eye display 120. obtain. Headset tracking module 114 may provide an estimated or predicted future position of near-eye display 120 to artificial reality engine 116 .

The artificial reality engine 116 executes an application within the artificial reality system environment 100 and provides near-eye display 120 position information, near-eye display 120 acceleration information, near-eye display 120 velocity information, near-eye display 120 predicted future , or any combination thereof, may be received from headset tracking module 114 . Artificial reality engine 116 may also receive inferred eye position and orientation information from eye tracking module 118 . Based on the information received, artificial reality engine 116 may determine content to provide on near-eye display 120 for presentation to the user. For example, if the information received indicates that the user looked left, the artificial reality engine 116 may generate content for the near-eye display 120 that reverses the user's eye movements in the virtual environment. . In addition, the artificial reality engine 116 implements actions within the application executing on the console 110 in response to action requests received from the input/output interface 140 and provides feedback to the user indicating that the actions have been performed. can be provided to The feedback can be visual or audible feedback via near-eye display 120 or tactile feedback via input/output interface 140 .

Eye tracking module 118 may receive eye tracking data from eye tracking unit 130 and determine the position of the user's eyes based on the eye tracking data. The eye position may include eye orientation, location, or both with respect to near-eye display 120, or any combination thereof. Determining the location of the eye within the orbit may allow the eye tracking module 118 to more accurately determine the orientation of the eye, since the axis of rotation of the eye varies as a function of the eye's location within the orbit. .

FIG. 2 is a perspective view of an example near-eye display in the form of an HMD device 200 for implementing some of the examples disclosed herein. HMD device 200 may be part of, for example, a VR system, an AR system, an MR system, or any combination thereof. HMD device 200 may include body portion 220 and head strap 230 . FIG. 2 shows the underside 223, front side 225, and left side 227 of the body portion 220 in perspective view. Head strap 230 may have an adjustable or stretchable length. There may be sufficient space between the body portion 220 of the HMD device 200 and the head strap 230 to allow the user to wear the HMD device 200 on the user's head. In various embodiments, HMD device 200 may include additional, fewer, or different components. For example, in some embodiments, HMD device 200 may include spectacle temples and temple tips, such as shown in FIG. 3 below, rather than head strap 230 .

HMD device 200 may present media to a user that includes virtual and/or augmented perspectives of physical real-world environments along with computer-generated elements. Examples of media presented by HMD device 200 include images (e.g., two-dimensional (2D) or three-dimensional (3D) images), video (e.g., 2D or 3D video), audio, or any combination thereof. obtain. Images and videos may be presented to each eye of the user by one or more display assemblies (not shown in FIG. 2) housed in body portion 220 of HMD device 200 . In various embodiments, one or more display assemblies may include a single electronic display panel or multiple electronic display panels (eg, one display panel for each eye of a user). Examples of electronic display panels may include, for example, LCDs, OLED displays, ILED displays, μLED displays, AMOLEDs, TOLEDs, some other displays, or any combination thereof. HMD device 200 may include two eyebox regions.

In some implementations, the HMD device 200 may include various sensors (not shown) such as depth sensors, motion sensors, position sensors, and eye tracking sensors. Some of these sensors may use structured light patterns for sensing. In some implementations, HMD device 200 may include an input/output interface for communication with a console. In some implementations, the HMD device 200 executes an application within the HMD device 200 to obtain depth information, position information, acceleration information, velocity information, predicted future position, or any of them of the HMD device 200. It may include a virtual reality engine (not shown) that can receive combinations from various sensors. In some implementations, information received by the virtual reality engine may be used to generate signals (eg, display instructions) to one or more display assemblies. In some implementations, HMD device 200 may include locators (such as locator 126, not shown) located in fixed positions on body portion 220 relative to each other and to a reference point. Each of the locators can emit light detectable by an external imaging device.

FIG. 3 is a perspective view of an example near-eye display 300 in the form of eyeglasses for implementing some of the examples disclosed herein. Near-eye display 300 may be a particular implementation of near-eye display 120 of FIG. 1 and may be configured to operate as a virtual reality display, an augmented reality display, and/or a mixed reality display. Near-eye display 300 may include frame 305 and display 310 . Display 310 may be configured to present content to a user. In some embodiments, display 310 may include display electronics and/or display optics. For example, as described above with respect to near-eye display 120 of FIG. 1, display 310 may include an LCD display panel, an LED display panel, or an optical display panel (eg, a waveguide display assembly).

Near-eye display 300 may further include various sensors 350 a , 350 b , 350 c , 350 d and 350 e on or within frame 305 . In some embodiments, sensors 350a-350e may include one or more depth sensors, motion sensors, position sensors, inertial sensors, or ambient light sensors. In some embodiments, sensors 350a-350e may include one or more image sensors configured to generate image data representing different fields of view in different directions. In some embodiments, the sensors 350a-350e are used to control or influence the displayed content of the near-eye display 300 and/or provide the user of the near-eye display 300 with an interactive VR/AR/MR experience. can be used as an input device to provide In some embodiments, sensors 350a-350e may also be used for stereoscopic imaging.

In some embodiments, near-eye display 300 may further include one or more lighting fixtures 330 to project light into the physical environment. The projected light may be associated with different frequency bands (eg, visible light, infrared light, ultraviolet light, etc.) and may serve various purposes. For example, luminaire 330 projects light in a dark environment (or an environment with low intensity infrared light, ultraviolet light, etc.) to cause sensors 350a-350e to capture images of different objects in the dark environment. can support. In some embodiments, lighting fixtures 330 may be used to project specific light patterns onto objects in the environment. In some embodiments, luminaire 330 may be used as a locator, such as locator 126 described above with respect to FIG.

In some embodiments, near-eye display 300 may also include high-definition camera 340 . Camera 340 may capture an image of the physical environment within its field of view. The captured image may be processed, for example, by a virtual reality engine (eg, artificial reality engine 116 of FIG. 1) to add virtual objects to the captured image or modify physical objects in the captured image, producing a processed image may be displayed to the user by display 310 for AR or MR applications.

FIG. 4 is a simplified diagram illustrating an example of an optical system within near-eye display system 400. As shown in FIG. Optical system 400 may include image source 410 and projector optics 420 . In the example shown in FIG. 4, image source 410 is in front of projector optics 420 . In various embodiments, image source 410 may be located outside the field of view of user's eye 490 . For example, one or more reflectors or directional couplers deflect light from an image source outside the field of view of the user's eye 490 so that the image source is located at image source 410 shown in FIG. Can be used to appear to be Light from areas (eg, pixels or light emitting devices) on image source 410 may be collimated and directed to exit pupil 430 by projector optics 420 . Thus, objects at different spatial locations on the image source 410 may appear to be objects far from the user's eye 490 at different viewing angles (FOV). Collimated light from different viewing angles can then be focused by the lens of the user's eye 490 onto different locations on the retina 492 of the user's eye 490 . For example, at least some portion of the light may be focused on the retina 492 to the fovea 494 . Collimated light rays from an area on image source 410 that enter user's eye 490 from the same direction may be focused to the same location on retina 492 . As such, a single image of image source 410 may be formed on retina 492 .

The user experience of using an artificial reality system depends on the field of view (FOV), image quality (e.g., angular resolution), eyebox size (to accommodate eye and head movements), and brightness of light within the eyebox. (or contrast) may depend on several properties of the optical system. Field of view describes the angular range of an image viewed by a user, usually measured in degrees, as viewed by one eye (for monocular HMDs) or both eyes (for either binocular or binocular HMDs). do. The human visual system may have a total binocular FOV of approximately 200° (horizontal) by 130° (vertical). To create a fully immersive visual environment, a large FOV (eg, greater than about 60°) can provide the feeling of being “inside” an image rather than just looking at it. A large FOV is desirable. A smaller field of view can also interfere with some important visual information. For example, an HMD system with a small FOV may use a gestural interface, but users cannot see their hands within the small FOV to be sure they are using the correct movements. A wider field of view, on the other hand, may require a larger display or optical system, which can affect the size, weight, cost, and comfort of the HMD.

Resolution refers to the angular size of a displayed pixel or image element appearing in front of a user, or the ability of a user to see and correctly interpret an object as imaged by one pixel and/or another. obtain. HMD resolution can be specified as the number of pixels on the image source for a given FOV value, from which angular resolution is the FOV in one direction divided by the number of pixels in the same direction on the image source. can be determined by For example, with a horizontal FOV of 40° and 1080 pixels in the horizontal direction on the image source, the corresponding angular resolution is approximately 2.2 minutes compared to the 1 minute resolution associated with Snellen 20/20 human visual acuity. obtain.

In some cases, the eyebox may be a two-dimensional box in front of the user's eyes from which the displayed image from the image source can be viewed. If the user's pupil moves outside the eyebox, the displayed image may not be seen by the user. For example, in a non-pupil shaping configuration, there is a viewing eyebox in which the non-vignette viewing of the HMD image source will reside, and the displayed image may be vignetted or clipped, but the user can still be visible when the pupil of the eye is outside the viewing eyebox. In a pupil-shaping configuration, the image may not be visible outside the exit pupil.

The fovea of the human eye, where the highest resolution can be achieved on the retina, can correspond to a FOV of about 2° to about 3°. This may require the eye to rotate in order to see off-axis objects with the highest resolution. Rotation of the eye to view off-axis objects can result in movement of the pupil as the eye rotates around a point approximately 10 mm behind the pupil. Additionally, the user cannot always accurately position the pupil of the user's eye (eg, having a radius of about 2.5 mm) at the ideal location within the eyebox. Furthermore, the environment in which the HMD is used may also affect the user's eye and/or head relative to the HMD, for example, when the HMD is used in a moving vehicle, or when the user is designed to be used while walking. The eyebox may need to be larger to allow movement of the eye. The amount of motion in these situations can depend on how tightly the HMD is coupled to the user's head.

Therefore, the HMD's optical system may need to provide a large enough exit pupil or viewing eyebox to view the entire FOV at full resolution to accommodate the movement of the user's pupil relative to the HMD. For example, in a pupil shaping configuration, a minimum size of 12mm to 15mm may be desired for the exit pupil. If the eyebox is too small, small misalignments between the eye and the HMD can result in at least partial loss of the image, and the user experience can be substantially compromised. In general, the lateral extent of the eyebox is more important than the vertical extent of the eyebox. This is due to significant differences in eye separation distances between users, as well as the fact that eyewear misalignment tends to occur more frequently in the lateral dimension, and that users adjust their line of sight more up or down than they do. may be due in part to the fact that it tends to adjust side to side, with greater amplitude and more frequently. Therefore, techniques that can increase the lateral dimension of the eyebox can substantially enhance the user's experience with an HMD. On the other hand, the larger the eyebox, the larger the optics and the heavier and more bulky the near-eye display device can be.

In order to view the displayed image against a bright background, the image source of the AR HMD may need to be sufficiently bright, and the optical system may allow the displayed image to be visible in backgrounds containing strong ambient light such as sunlight. As such, it may need to be efficient in providing a bright image to the user's eye. The HMD's optical system can be designed to focus light within the eyebox. When the eyebox is large, a high power image source can be used to provide a bright image visible within the large eyebox. Thus, there can be tradeoffs between eyebox size, cost, brightness, optical complexity, image quality, and the size and weight of the optical system.

FIG. 5 illustrates an example optical see-through augmented reality system 500 including a waveguide display for exit pupil expansion, according to certain embodiments. Augmented reality system 500 may include projector 510 and combiner 515 . Projector 510 may include a light source or image source 512 and projector optics 514 . In some embodiments, light source or image source 512 may include one or more micro LED devices. In some embodiments, image source 512 may include a plurality of pixels that display virtual objects, such as an LCD display panel or LED display panel. In some embodiments, image source 512 may include a light source that produces coherent or partially coherent light. For example, the light source 512 may include laser diodes, vertical cavity surface emitting lasers, LEDs, superluminescent LEDs (sLEDs), and/or microLEDs as described above. In some embodiments, image source 512 is a plurality of light sources (eg, an array of LEDs described above) each emitting monochromatic image light corresponding to a primary color (eg, red, green, or blue). can include In some embodiments, image source 512 can include three two-dimensional arrays of microLEDs, each two-dimensional array of microLEDs emitting light in a primary color (eg, red, green, or blue). It may include micro LEDs configured to: In some embodiments, image source 512 may include an optical pattern generator such as a spatial light modulator. Projector optics 514 are one or more that can condition light from image source 512 , such as expanding, collimating, scanning, or projecting light from image source 512 to combiner 515 . of optical components. The one or more optical components may include, for example, one or more lenses, liquid lenses, mirrors, free optics, apertures, and/or gratings. For example, in some embodiments, image source 512 may include one or more one-dimensional arrays or elongated two-dimensional arrays of micro LEDs, and projector optics 514 may illuminate the micro LEDs to generate image frames. may include one or more one-dimensional scanners (eg, micromirrors or prisms) configured to scan a one-dimensional array of or elongated two-dimensional arrays. In some embodiments, projector optics 514 may include a liquid lens (eg, a liquid crystal lens) with multiple electrodes that allow light from image source 512 to be scanned.

Combiner 515 may include an input coupler 530 for coupling light from projector 510 into substrate 520 of combiner 515 . Input coupler 530 may include a volume holographic grating or another diffractive optical element (DOE) (eg, surface relief grating (SRG)), a tilted reflective surface of substrate 520, or a refractive coupler (eg, wedge or prism). . For example, input coupler 530 may include a reflective volume Bragg grating or a transmissive volume Bragg grating. Input coupler 530 may have a coupling efficiency of 30%, 50%, 75%, 90%, or more for visible light. Light coupled into substrate 520 may propagate within substrate 520 through, for example, total internal reflection (TIR). Substrate 520 may be in the form of an eyeglass lens. Substrate 520 may have a flat or curved surface and may be made of one or more types of dielectric material such as glass, quartz, plastic, polymer, poly(methylmethacrylate) (PMMA), quartz, ceramic, or the like. can contain. Substrate thicknesses can range, for example, from less than about 1 mm to about 10 mm or more. Substrate 520 may be transparent to visible light.

Substrate 520 may include or be coupled to a plurality of output couplers 540, each extracting and extracting from substrate 520 at least a portion of the light directed by and propagating within substrate 520. The light 560 is configured to be directed to an eyebox 595 in which the eye 590 of the user of the augmented reality system 500 may be located when the augmented reality system 500 is in use. Multiple output couplers 540 may replicate the exit pupil to increase the size of eyebox 595 so that the displayed image may be visible in a larger area. Like input coupler 530, output coupler 540 may include grating couplers (eg, volume holographic gratings or surface relief gratings), other diffractive optical elements (DOEs), prisms, and the like. For example, output coupler 540 may include a reflective volume Bragg grating or a transmissive volume Bragg grating. Output coupler 540 may have different coupling (eg, diffraction) efficiencies at different locations. Substrate 520 also allows light 550 from the environment before combiner 515 to pass through with little loss. Output coupler 540 may also allow light 550 to pass through with little loss. For example, in some implementations, output coupler 540 may have a very low diffraction efficiency of light 550 such that light 550 may be refracted or otherwise pass through output coupler 540 with little loss. , and therefore may have a higher intensity than the extracted light 560 . In some implementations, output coupler 540 may have a high diffraction efficiency of light 550 and may diffract light 550 into a particular desired direction (ie, diffraction angle) with little loss. As a result, the user may be able to see a combined image of the environment in front of combiner 515 and the image of the virtual object projected by projector 510 . In some implementations, output coupler 540 may have high diffraction efficiency of light 550 and may diffract light 550 into a particular desired direction (eg, diffraction angle) with little loss.

In some embodiments, projector 510 , input coupler 530 and output coupler 540 may be on any side of substrate 520 . Input coupler 530 and output coupler 540 are reflective gratings (also called reflective gratings) or transmissive gratings (also called transmission gratings) to couple display light into or out of substrate 520 . may be called).

FIG. 6 illustrates an example optical see-through augmented reality system 600 including a waveguide display for exit pupil expansion, according to certain embodiments. Augmented reality system 600 may be similar to augmented reality system 500 and may include a waveguide display and a projector that may include a light source or image source 612 and projector optics 614 . A waveguide display may include a substrate 630 , an input coupler 640 and a plurality of output couplers 650 as described above with respect to augmented reality system 500 . FIG. 5 only shows the propagation of light from a single field of view, whereas FIG. 6 shows the propagation of light from multiple fields of view.

FIG. 6 shows that the exit pupil is replicated by output coupler 650 to form a collective exit pupil or eyebox, with different fields of view (eg, different pixels on image source 612) leading to different respective eyeboxes. , and light from the same field of view (eg, the same pixel on image source 612) may have the same propagation direction for different individual exit pupils. Thus, a single image of image source 612 can be formed by a user's eye located anywhere within the eyebox, and light propagating in the same direction from different individual exit pupils will appear in the same image on image source 612 . It can be from pixels and focused to the same location on the retina of the user's eye. FIG. 6 shows that an image of the image source can be seen by the user's eyes even though the user's eyes move to different locations within the eyebox.

In many waveguide-based near-eye display systems, two or more output gratings direct the display light in two dimensions, or two It can be used for axial expansion (which may be referred to as biaxial pupil expansion). The two gratings have different grating parameters such that one grating can be used to replicate the exit pupil in one direction and the other grating can be used to replicate the exit pupil in another direction. can.

を有し得る体積ホログラフィック格子または表面レリーフ格子であってもよく、式中、ｄは、格子の厚さであり、λは、自由空間内の入射光の波長であり、Λは、格子周期であり、ｎは、記録媒体の屈折率である。Ｋｌｅｉｎ－ＣｏｏｋパラメータＱは、格子による光回折を３つのレジームに分割し得る。格子がＱ＜＜１によって特徴付けられるとき、格子による光回折は、Ｒａｍａｎ－Ｎａｔｈ回折と称され得、複数の回折次数が、垂直および／または斜入射光の場合に発生し得る。格子がＱ＞＞１（例えば、Ｑ≧１０）によって特徴付けられるとき、格子による光回折は、ブラッグ回折と称され得、一般的にはゼロ次および±１回折次数が、ブラッグ条件を満足する角度で格子に入射する光の場合に発生し得る。格子がＱ≒１によって特徴付けられるとき、格子による回折は、Ｒａｍａｎ－Ｎａｔｈ回折とブラッグ回折との間であり得る。ブラッグ条件を満たすため、格子の厚さｄは、媒体の体積を占有するために（表面においてではなく）特定の値よりも高くてもよく、故に、体積ブラッグ格子と称され得る。ＶＢＧは、一般的に、比較的小さい屈折率変調（例えば、Δｎ≦０．０５）ならびに高いスペクトルおよび角度選択性を有し得る一方、表面レリーフ格子は、一般的に、大きい屈折率変調（例えば、Δｎ≧０．５）ならびに幅広のスペクトルおよび角度バンド幅を有し得る。 As explained above, the input and output grating couplers described above have very different Klein-Cook parameters Q:

where d is the thickness of the grating, λ is the wavelength of the incident light in free space, and Λ is the grating period and n is the refractive index of the recording medium. The Klein-Cook parameter Q can divide optical diffraction by a grating into three regimes. Optical diffraction by a grating can be referred to as Raman-Nath diffraction when the grating is characterized by Q<<1, and multiple diffraction orders can occur for normal and/or grazing incidence light. Optical diffraction by a grating can be referred to as Bragg diffraction when the grating is characterized by Q>>1 (eg, Q≧10), and generally the zero and ±1 diffraction orders satisfy the Bragg condition. It can occur for light incident on the grating at an angle. When the grating is characterized by Q≈1, the diffraction by the grating can be between Raman-Nath diffraction and Bragg diffraction. To satisfy the Bragg condition, the thickness d of the grating may be higher than a certain value (not at the surface) to occupy the volume of the medium, hence it may be called a volume Bragg grating. VBGs can typically have relatively small refractive index modulations (e.g., Δn≤0.05) and high spectral and angular selectivities, while surface relief gratings typically have large refractive index modulations (e.g., , Δn≧0.5) and broad spectral and angular bandwidths.

FIG. 7A illustrates the spectral bandwidth of an example volume Bragg grating (eg, reflective VBG) and the spectral bandwidth of an example surface relief grating (eg, transmissive SRG). The horizontal axis represents the wavelength of incident visible light and the vertical axis corresponds to diffraction efficiency. As shown by curve 710, the diffraction efficiency of the reflected VBG is high in a narrow wavelength range such as green light. In contrast, the diffraction efficiency of transmissive SRGs can be high over a very wide wavelength range, such as blue-red light, as shown by curve 720 .

FIG. 7B illustrates the angular bandwidth of an example volume Bragg grating (eg, reflective VBG) and the angular bandwidth of an example surface relief grating (eg, transmissive SRG). The horizontal axis represents the angle of incidence of visible light incident on the grating and the vertical axis corresponds to diffraction efficiency. As shown by curve 715, the diffraction efficiency of the reflected VBG is high for light incident on the grating from a narrow range of angles, such as about ±2.5° from the perfect Bragg condition. In contrast, the diffraction efficiency of the transmissive SRG is high over a very wide angular range, such as greater than about ±10° or wider, as shown by curve 725 .

Due to the high spectral selectivity in the Bragg condition, VBGs such as reflective VBGs can enable single waveguide designs without crosstalk between primary colors and can exhibit excellent see-through quality. However, spectral and angular selectivity may result in lower efficiency since only a portion of the display light within the entire FOV may be diffracted and reach the user's eye.

FIG. 8A illustrates an example optical see-through augmented reality system including a waveguide display 800 and surface relief gratings for exit pupil expansion, according to certain embodiments. Waveguide display 800 may include substrate 810 (eg, a waveguide), which may be similar to substrate 520 . Substrate 810 may be transparent to visible light and may include, for example, glass, quartz, plastic, polymer, PMMA, ceramic, quartz substrates. Substrate 810 may be a flat substrate or a curved substrate. Substrate 810 can include a first surface 812 and a second surface 814 . Display light may be coupled into substrate 810 by input coupler 820 and reflected by first surface 812 and second surface 814 through total internal reflection such that the display light may propagate within substrate 810 . . As described above, input coupler 820 may include a grating, a refractive coupler (eg, wedge or prism), or a reflective coupler (eg, a reflective surface having an oblique angle with respect to substrate 810). For example, in one embodiment, input coupler 820 can include a prism that can couple different colors of display light into substrate 810 at the same refraction angle. In another example, input coupler 820 can include a grating coupler that can diffract different colors of light into substrate 810 in different directions. Input coupler 820 may have a coupling efficiency of 10%, 20%, 30%, 50%, 75%, 90%, or more for visible light.

Waveguide display 800 uses one or two surfaces (eg, second It may include a first grating 830 and a second grating 840 positioned on one surface 812 and second surface 814). The first grating 830 may be configured to expand at least a portion of the display light beam along one direction, such as approximately the x-direction. Display light coupled into substrate 810 may propagate in the direction indicated by line 832 . Display light propagates in substrate 810 along the direction indicated by lines 832 , but a portion of the display light is propagated by lines 834 each time display light propagating in substrate 810 reaches first grating 830 . As shown, it can be diffracted by a portion of first grating 830 toward second grating 840 . Second grating 840 then extracts display light from first grating 830 by diffracting a portion of the display light propagating in substrate 810 into the eyebox each time it reaches second grating 840 . may be scaled in different directions (eg, about the y-direction). In the second grating 840, the exit region 850 is the area where the display light for the entire FOV at one pupil location within the eyebox (e.g., the center of the eyebox) can be coupled out of the waveguide display 800. show.

FIG. 8B illustrates an example of an eyebox containing a two-dimensional replicated exit pupil. FIG. 8B shows that a single input pupil 805 can be replicated by a first grating 830 and a second grating 840 to form a collective exit pupil 860 that includes a two-dimensional array of individual exit pupils 852. show. For example, the exit pupil may be replicated approximately in the x-direction by a first grating 830 and approximately in the y-direction by a second grating 840 . As explained above, output light propagating in the same direction from individual exit pupils 852 may be focused to the same location within the retina of the user's eye. A single image can thus be formed by the user's eye from the output light within the two-dimensional array of individual exit pupils 852 .

FIG. 9A illustrates the wavevectors of diffracted light and the exit pupil for multiple colors by an example surface relief grating for exit pupil expansion in a waveguide display. A circle 910 may represent a wave vector of light that may be guided by the waveguide. For light with wavevectors outside the circle 910, the light can become evanescent. A circle 920 may represent the wavevector of light that may leak out of the waveguide because the total internal reflection condition is not met. Thus, the rings between circles 910 and 920 may represent wavevectors of light that may be guided by the waveguide and propagate within the waveguide through TIR. Wavevector 932 indicates the light dispersion caused by the input grating, and different colors of light may have different wavevectors and different diffraction angles. Wavevector 942 represents the light dispersion caused by the front grating (eg, first grating 830), and different colors of light may have different diffraction angles. Wavevector 952 indicates the light dispersion caused by the back grating (eg, second grating 840), and different colors of light may have different diffraction angles. Wavevectors of each color may form respective closed triangles, and triangles of different colors may share a common original vertex 922 . Therefore, the total variance due to the three grids can be close to zero.

Even though the overall dispersion due to the three gratings can be zero, the dispersion due to each grating is , can cause a reduction or clipping of the waveguide display's field of view. For example, in FOV 924, the footprint of the FOV after diffraction by the input grating may be different for different colors due to dispersion by the input grating. In the example shown in FIG. 9A, the FOV footprint 936 for the first color of light may be located within the ring, while a portion of the FOV footprint 934 for the second color of light and the first A portion of the FOV footprint 938 for color 3 light may fall outside the ring and thus may not be guided by the waveguide. In addition, the FOV footprint after diffraction by the front grating can be further clipped or reduced. In the example shown in FIG. 9A, a small portion of FOV footprint 946 for light of a first color, a large portion of FOV footprint 944 for light of a second color, and a third color Most of the FOV footprint 948 for light may fall outside the annulus and thus may not be guided by the waveguide and diffracted by the back grating to reach the exit pupil.

FIG. 9B illustrates field clipping with an example surface relief grating for exit pupil expansion in a waveguide display. For example, the FOV for the first color of light after diffraction by the back grating may be indicated by footprint 956, which may be close to the full FOV. For light of the second color, the top portion of the FOV may be clipped after diffraction by the first grating and the right portion of the FOV may be clipped after diffraction by the front grating. Thus, the FOV for the second color light after diffraction by the back grating may be indicated by footprint 954, which may be much smaller than the full FOV. Similarly, for light of the third color, the bottom portion of the FOV may be clipped after diffraction by the first grating and the left portion of the FOV may be clipped after diffraction by the front grating. Hence, the FOV for the third color light after diffraction by the back grating may be indicated by footprint 958, which may be much smaller than the full FOV. Therefore, certain color components of the image may be missing in certain fields of view. As such, two or more waveguides and corresponding gratings can be used to achieve a full FOV for different colors. In addition, as explained above, the wide bandwidth of the SRG can cause crosstalk between lights of different primary colors and/or from different FOVs, so multiple waveguides can also cause crosstalk. can be used to avoid

Due to the high spectral selectivity in the Bragg condition, VBGs such as reflective VBGs can enable single waveguide designs without crosstalk between primary colors in volume Bragg gratings and can achieve excellent see-through quality. . Thus, input coupler 530 or 640 and output coupler 540 or 650 may comprise volume Bragg gratings that direct the holographic recording material into light patterns generated by interference between two or more coherent light beams. It may be a volume hologram recorded in a holographic recording material by exposure. In a volume Bragg grating, the incident angle and wavelength of incident light may need to satisfy the Bragg phase matching condition so that the incident light is diffracted by the Bragg grating. When a single Bragg grating is used in a waveguide-based near-eye display, the spectral and angular selectivity of the volume Bragg grating is such that only a portion of the display light can be diffracted and reach the user's eye. It may result in lower efficiency, and the field of view and operating wavelength range of waveguide-based near-eye displays may be limited. In some embodiments, multiplexed VBGs can be used to improve efficiency and increase FOV.

FIG. 10A is a front view of an example volume Bragg grating-based waveguide display 1000, in accordance with certain embodiments. Waveguide display 1000 may include substrate 1010 , which may be similar to substrate 520 . Substrate 1010 may be transparent to visible light and may include, for example, glass, quartz, plastic, polymer, PMMA, ceramic, quartz substrates. Substrate 1010 can be a flat substrate or a curved substrate. Substrate 1010 can include a first surface 1012 and a second surface 1014 . Display light may be coupled into substrate 1010 by input coupler 1020 and reflected by first surface 1012 and second surface 1014 through total internal reflection such that the display light may propagate within substrate 1010. . As described above, input coupler 1020 can be a diffractive coupler (eg, volume holographic grating or surface relief grating), a refractive coupler (eg, wedge or prism), or a reflective coupler (eg, tilted with respect to substrate 1010). angled reflective surfaces). For example, in one embodiment, input coupler 1020 can include a prism that can couple different colors of display light into substrate 1010 at the same refraction angle. In another example, the input coupler can include a grating coupler that can diffract different colors of light into the substrate 1010 in different directions.

Waveguide display 1000 uses one or two surfaces (e.g., first surface 1012 and second surface 1012) of substrate 1010 to expand an incident display light beam in two dimensions to fill an eyebox with display light. may include a first grating 1030 and a second grating 1040 positioned on the surface 1014 of the . First gratings 1030 direct at least a portion of a display light beam (eg, light corresponding to a particular field of view and/or wavelength range) each in one direction, as indicated by lines 1032, 1034, and 1036. It may include one or more multiplexed volume Bragg gratings configured to expand along. For example, while display light propagates in substrate 1010 along directions indicated by lines 1032 , 1034 , or 1036 , a portion of the display light reaches first grating 1030 as display light propagating in substrate 1010 reaches first grating 1030 . Each time, it can be diffracted by the first grating 1030 to the second grating 1040 . The second grating 1040 then extracts the display light from the first grating 1030 by diffracting a portion of the display light propagating in the substrate 1010 into the eyebox each time it reaches the second grating 1040 . can be expanded in different directions. In the second grating 1040, the exit region 1050 is the area where the display light for the entire FOV at one pupil location within the eyebox (eg, the center of the eyebox) can be coupled out of the waveguide display 1000. show.

As explained above, the first grating 1030 and the second grating 1040 may each include multiplexed VBGs containing multiple VBGs each designed for a particular FOV range and/or wavelength range. . For example, the first grating 1030 may include hundreds or more VBGs (eg, about 300 to about 1000 VBGs) recorded by hundreds or more exposures, and each VBG may be recorded under different conditions. The second grating 1040 may also include tens or hundreds of VBGs (eg, 50 or more VBGs) recorded by tens or hundreds of exposures. First grating 1030 and second grating 1040 can each be a transmission grating or a reflection grating.

10B and 10C illustrate top and side views, respectively, of a volume Bragg grating-based waveguide display 1000. FIG. Input coupler 1020 may include projector optics (not shown, eg, lenses) and prisms. The display light may be collimated and projected onto the prism by the projector optics and coupled into the substrate 1010 by the prism. The prisms may have a refractive index that matches the refractive index of substrate 1010 such that light coupled into substrate 1010 may be incident on surface 1012 or 1014 of substrate 1010 at an angle of incidence greater than the critical angle of substrate 1010. may include wedges with specific angles such as; As such, display light coupled into the substrate 1010 can be guided by the substrate 1010 through total internal reflection and reflected by the plurality of regions of the first grating 1030 to the second, as described above. It can be diffracted towards grating 1040 . A second grating 1040 may then diffract the display light out of the substrate 1010 in multiple regions to replicate the exit pupil.

FIG. 11 illustrates light dispersion in an example volume Bragg grating-based waveguide display, such as waveguide display 1000, in accordance with certain embodiments. As shown in the example, sphere 1110 may represent the wavevector of light that may be guided by the waveguide. For light with wavevectors outside the sphere 1110, the light can become evanescent. Cone 1120 may represent a wave vector of light that may leak out of the waveguide because the total internal reflection condition is not met. Thus, the region of sphere 1110 outside cone 1120 may represent a wave vector of light that may be guided by a waveguide and propagate within the waveguide through TIR. Point 1130 may represent the wave vector of display light coupled into the waveguide, eg, by a prism. Wavevector 1140 shows the light dispersion caused by first grating 1030, and different colors of light may have different diffraction angles. Wavevector 1150 shows the light dispersion caused by second grating 1040, and different colors of light may have different diffraction angles. Thus, the light coupled out of the substrate may have some dispersion so that images of different colors may form one image without completely overlapping each other. Therefore, the displayed image may be blurred and the resolution of the displayed image may be reduced.

FIG. 12A illustrates an example volume Bragg grating 1200 . The volume Bragg grating 1200 shown in FIG. 12A can include a transmission holographic grating having a thickness D. FIG. The refractive index n of volume Bragg grating 1200 may be modulated with an amplitude Δn, and the grating period of volume Bragg grating 1200 may be Λ. Incident light 1210 having wavelength λ may enter volume Bragg grating 1200 at an angle of incidence θ and may be refracted into volume Bragg grating 1200 as incident light 1220 propagating within volume Bragg grating 1200 at angle θ _n . Incident light 1220 may be diffracted by volume Bragg grating 1200 into diffracted light 1230 , which may propagate within volume Bragg grating 1200 at a diffraction angle θ _d and exit volume Bragg grating 1200 as diffracted light 1240 . can be refracted into

を表し得、ここで、

である。ベクトル１２２５は、

を表し得、ベクトル１２３５は、

を表し得、ここで、

である。ブラッグ位相整合条件下では、

である。故に、所与の波長λの場合、ブラッグ条件を完璧に満たす、入射角θ（またはθ_ｎ）および回折角度θ_ｄの１つのペアのみが存在し得る。同様に、所与の入射角θの場合、ブラッグ条件を完璧に満たす１つの波長λが存在し得る。そのようなものとして、回折は、小さい波長範囲について、および完璧なブラッグ条件周辺の小さい入射角範囲において発生し得る。体積ブラッグ格子１２００の回折効率、波長選択性、および角度選択性は、体積ブラッグ格子１２００の厚さＤの関数であり得る。例えば、ブラッグ条件周辺の体積ブラッグ格子１２００の半値全幅（ＦＷＨＭ）波長範囲およびＦＷＨＭ角度範囲は、体積ブラッグ格子１２００の厚さＤに反比例し得るが、ブラッグ条件での最大回折効率は、ｓｉｎ^２（ａ×Δｎ×Ｄ）の関数であり得、式中、ａは、係数である。反射体積ブラッグ格子では、ブラッグ条件での最大回折効率は、ｔａｎｈ^２（ａ×Δｎ×Ｄ）の関数であり得る。 FIG. 12B illustrates the Bragg conditions for the volume Bragg grating 1200 shown in FIG. 12A. Volume Bragg grating 1200 may be a transmission grating. Vector 1205 is

, where

is. Vector 1225 is

and the vector 1235 is

, where

is. Under the Bragg phase matching condition,

is. Therefore, for a given wavelength λ, there can only be one pair of incident angle θ (or θ _n ) and diffraction angle θ _d that perfectly satisfies the Bragg condition. Similarly, for a given angle of incidence θ, there may be one wavelength λ that perfectly satisfies the Bragg condition. As such, diffraction can occur for a small range of wavelengths and for a small range of incident angles around the perfect Bragg condition. The diffraction efficiency, wavelength selectivity, and angular selectivity of volume Bragg grating 1200 can be a function of the thickness D of volume Bragg grating 1200 . For example, the full width half maximum (FWHM) wavelength range and FWHM angular range of the volume Bragg grating 1200 around the Bragg condition can be inversely proportional to the thickness D of the volume Bragg grating 1200, whereas the maximum diffraction efficiency at the Bragg condition is sin ² ( a×Δn×D), where a is a coefficient. For a reflective volume Bragg grating, the maximum diffraction efficiency under the Bragg condition can be a function of tanh ² (a×Δn×D).

As explained above, in some designs each a different color (e.g., R, G, or B) and/or multiple polymer layers containing Bragg gratings for different FOVs can be arranged in a stack to couple display light to the user's eye. In some designs, multiplexed Bragg gratings may be used, where each portion of the multiplexed Bragg grating may be used to diffract light within different FOV ranges and/or different wavelength ranges. Thus, in some designs, several hundred or more than a thousand, etc., each to achieve the desired diffraction efficiency and large FOV for the entire visible spectrum (eg, from about 400 nm to about 700 nm, or from about 450 nm to about 650 nm). , one or more thick volume Bragg gratings may be used, including mass gratings (or holograms) recorded by mass exposure (eg, holographic recording).

A VBG or other holographic optical element as described above may be recorded in a layer of holographic material (eg, photopolymer). In some embodiments, the VBG can be recorded first and then laminated to the substrate in the near-eye display system. In some embodiments, a holographic material layer can be coated or laminated to a substrate and then a VBG can be recorded in the holographic material layer.

In general, to record a holographic optical element in a photosensitive material layer, two coherent beams can interfere with each other at specific angles to produce a unique interference pattern within the photosensitive material layer, which in turn , may produce a unique refractive index modulation pattern in the photosensitive material layer, which refractive index modulation pattern may correspond to the light intensity pattern of the interference pattern. Photosensitive material layers can include, for example, silver halide emulsions, dichromated gelatin, photopolymers containing photopolymerizable monomers suspended in a polymer matrix, photorefractive crystals, and the like. An example of a photosensitive material layer for holographic recording can include a matrix precursor that can be precured to form a polymeric binder prior to holographic recording and writing monomers for holographic recording. It is a stepped photopolymer.

In one example, the photosensitive material layer can include a polymeric binder, a monomer (eg, an acrylic monomer), and an initiator such as an initiator, chain transfer agent, or photosensitive dye. A polymeric binder can act as a support matrix. Monomers may be dispersed within the support matrix and may serve as refractive index modulators. Photosensitive dyes can absorb light and interact with initiators to polymerize the monomers. Thus, at each exposure (recording), the interference pattern creates concentration and density gradients that can cause polymerization and diffusion of monomers to bright fringes, resulting in refractive index modulation. For example, areas with higher concentrations of monomer and polymerization may have a higher refractive index. As exposure and polymerization progress, less monomer may be available for polymerization and diffusion may be suppressed. After all or substantially all of the monomer has been polymerized, there may be no new gratings recorded in the photosensitive material layer. Display haze can be significant in thick VBGs containing large gratings recorded in large exposures.

As explained above, in some waveguide-based near-eye display systems, two output gratings (or two grating layers or multiplexing) are used to enlarge the eyebox of the waveguide-based near-eye display. Two portions of the grating) can generally be used to expand display light in two dimensions or along two axes for biaxial pupil expansion. Spatially separating the two output gratings and reducing the total number of exposures for each output grating allows the see-through region (e.g., the center) of a waveguide-based near-eye display to contain only one output grating. As such, it can help reduce display haze. For example, in some embodiments, the first output grating can be recorded with more exposures (eg, >500 or >1000 times) and positioned outside the see-through area of the waveguide-based near-eye display. obtain. A second output grating can be recorded with fewer exposures (eg, <100 or <50 times) and can be positioned in the see-through region of a waveguide-based near-eye display. Therefore, display haze in the see-through area can be significantly reduced. However, due to the spatial separation of the two output gratings, the overall size of waveguide-based near-eye displays can be very large.

The grating couplers described above can include transmissive or reflective VBGs that can have some similar features and some different features. For example, as explained above, the FWHM wavelength range and FWHM angular range of a transmissive or reflective volume Bragg grating near the Bragg condition can be inversely proportional to the thickness D of the transmissive or reflective volume Bragg grating. The maximum diffraction efficiency in the Bragg condition for transmissive VBG can be a function of sin ² (a×Δn×D), where a is the coefficient and Δn is the refractive index modulation, but the reflective The maximum diffraction efficiency under the Bragg condition for VBG can be a function of tanh ² (a×Δn×D). In addition, the parameters of the transmission and reflection volume Bragg gratings (e.g., grating tilt angle) can be used to couple display light into the waveguide at a particular angle such that the coupled display light can be guided by the waveguide through TIR. can vary to Due to the different grating parameters, the dispersion characteristics of transmission and reflection gratings can be different.

FIG. 13A illustrates a front view of an example volume Bragg grating-based waveguide display 1300 with exit pupil expansion and dispersion reduction, in accordance with certain embodiments. FIG. 13B illustrates a side view of an example volume Bragg grating-based waveguide display 1300 with exit pupil expansion and dispersion reduction, in accordance with certain embodiments. Waveguide display 1300 may be similar to waveguide display 1000 and may include input coupler 1320 in a different location compared to input coupler 1020 . Waveguide display 1300 may include a substrate 1310 and first and second gratings 1330 and 1340 formed on or within substrate 1310 . Like input coupler 1020 , input coupler 1320 may include projector optics 1322 (eg, lenses) and prism 1324 . Display light may be coupled into substrate 1310 by input coupler 1320 and guided by substrate 1310 . The display light may reach the first portion 1332 of the first grating 1330, be diffracted by the first portion 1332 of the first grating 1330, change the direction of propagation, and reach another portion of the first grating 1330. Each of these other portions can reach and diffract the display light towards the second grating 1340 . A second grating 1340 may diffract the display light out of the substrate 1310 at different locations to form multiple exit pupils as described above.

Each of the first portion 1332 and the other portion of the first grating 1330 has a matching grating vector (eg, the same grating vector in the xy plane and the same grating vector in the z direction, opposite grating vector , or have both the same and opposite grating vectors, but recorded with different exposure durations to achieve different diffraction efficiencies). Therefore, due to the opposite Bragg conditions of diffraction (eg, +1st and −1st orders of diffraction) in each of the first portion 1332 and the other portion of the first grating 1330 , they are diffracted by each other. Dispersion can be compensated to reduce overall dispersion. Accordingly, the overall dispersion of display light by waveguide display 1300 can be reduced in at least one direction.

FIG. 14A illustrates the propagation of light from different fields of view in a reflective volume Bragg grating-based waveguide display 1400, according to certain embodiments. Waveguide display 1400 may include reflective VBG 1410 . Due to the grating tilt angle and hence the grating vector of reflective VBG 1410 , light from the positive field (indicated by lines 1422 ) has a smaller angle of incidence on the fringes of reflective VBG 1410 and also on top surface 1402 of waveguide display 1400 . can have a smaller angle of incidence. On the other hand, light from the negative field of view (indicated by line 1424) may have a larger angle of incidence on the fringes of reflective VBG 1410 and also a larger angle of incidence on top surface 1402 of waveguide display 1400. FIG.

FIG. 14B illustrates the propagation of light from different fields of view in a transmissive volume Bragg grating-based waveguide display 1450, according to certain embodiments. Waveguide display 1450 may include transmissive VBG 1460 . Due to the grating tilt angle difference, the transmissive VBG 1460 may diffract light from different fields of view in a different manner compared to the reflective VBG 1410 . For example, as illustrated, light from the positive field of view (indicated by line 1472) may have a smaller angle of incidence with respect to the fringes of transmissive VBG 1460, but with respect to lower surface 1452 of waveguide display 1450. can have a larger angle of incidence. On the other hand, light from the negative field (indicated by line 1474) may have a larger angle of incidence on the fringes of the transmissive VBG 1460, but a smaller angle of incidence on the bottom surface 1452 of the waveguide display 1450. . The manner in which light is diffracted from different fields of view by reflection or transmission gratings can affect the parameters and performance of waveguide displays.

FIG. 15 illustrates an example of a reflective volume Bragg grating-based waveguide display 1500 with exit pupil expansion and dispersion reduction, in accordance with certain embodiments. Waveguide display 1500 may include upper grating 1505 and lower grating 1515 . In the illustrated example, the upper grating 1505 may be a reflective VBG and the lower grating 1515 may also be a reflective grating. In lower grating 1515, exit region 1550 represents the area where display light for the entire FOV at one pupil location within the eyebox (eg, the center of the eyebox) may be coupled out of the lower grating. As shown in FIG. 15, the upper FOV at the exit region 1550 represented by the line between the upper right corner 1522 and the upper left corner 1524 may map to the curve 1530 on the upper grid 1505, and the upper right corner of the exit region 1550 1522 and upper left corner 1524 may map to locations 1532 and 1534 on top grid 1505, respectively. The lower FOV at the exit region 1550 represented by the line between the lower right corner 1542 and the lower left corner 1544 may map to the curve 1510 on the lower grid 1505 such that the lower right corner 1542 and the lower left corner 1544 of the exit region 1550 are It may map to location 1512 and location 1514 on lower grid 1505 . Therefore, if curve 1530 is below the line between upper right corner 1522 and upper left corner 1524 of exit region 1550, there may be some FOV clipping. As such, curve 1530 may be above the line between upper right corner 1522 and upper left corner 1524 of exit region 1550 to protect the entire FOV. Therefore, the size of waveguide display 1500 can be large.

FIG. 16 illustrates an example transmissive volume Bragg grating-based waveguide display 1600 with exit pupil expansion and form factor reduction, in accordance with certain embodiments. Waveguide display 1600 may include upper grating 1605 and lower grating 1615 . In the illustrated example, top grating 1605 may be a reflective VBG and bottom grating 1615 may be a transmissive VBG. In lower grating 1615, exit region 1650 represents the area where display light for the entire FOV at one pupil location within the eyebox (eg, the center of the eyebox) may be coupled out of the lower grating. As shown in FIG. 16, the upper FOV at the exit region 1650 represented by the line between the upper right corner 1622 and the upper left corner 1624 may map to the curve 1610 on the upper grid 1605 and the upper right corner of the exit region 1650. 1622 and upper left corner 1624 may map to location 1612 and location 1614 on upper grid 1605, respectively. The lower FOV at exit region 1650 represented by the line between lower right corner 1642 and lower left corner 1644 may map to curve 1630 on lower grid 1605 such that lower right corner 1642 and lower left corner 1644 of exit region 1650 are It may map to location 1632 and location 1634 on lower grid 1605 . Therefore, there may be some overlap between upper grating 1605 and lower grating 1615 to reduce the overall size of waveguide display 1600 . For example, location 1632 may be lower than upper right corner 1622 and still map to lower right corner 1642 .

FIG. 17A illustrates an example transmissive volume Bragg grating 1700 in a waveguide display, according to certain embodiments. The grating tilt angle α of the transmissive VBG 1700 may need to be within a certain range to transmissively diffract the display light. For example, if the grating tilt angle α of the transmissive VBG 1700 is less than a certain value, the transmissive VBG 1700 may become a reflected VBG, and the distance between two consecutive locations where the display light can reach the grating is too large. (and thus the exit pupil can be sparsely replicated in the eyebox) or the display light can be evanescent. Therefore, the grating tilt angle α of the transmissive VBG 1700 must be greater than a certain value to transmissively diffract the display light.

FIG. 17B illustrates an example of a transmissive VBG 1710 in a waveguide display, where light diffracted by the transmissive VBG may not be fully reflected and guided within the waveguide. The grating tilt angle α of the transmissive VBG 1710 may be greater than a certain value, such as greater than about 60°. As such, light coupled into the waveguide may strike the surface of the waveguide at an angle of incidence less than the critical angle, and thus be completely reflected and not guided within the waveguide. There is Therefore, the grating tilt angle α of the transmitted VBG is also set to a certain value (eg, about 60° ). As such, the grating tilt angle α of the transmitted VBG may need to be within a certain range.

FIG. 17C illustrates an example reflective volume Bragg grating 1750 in a waveguide display, according to certain embodiments. The grating tilt angle α of the reflective VBG 1750 may also need to be within a certain range to reflectively diffract the display light. If the grating tilt angle α of the reflected VBG 1750 is greater than a certain value, the reflected VBG 1750 may become a transmitted VBG and the distance between two consecutive locations where the display light can reach the grating may be too large. (and thus the exit pupil may be sparsely replicated in the eyebox) or the display light may become evanescent. Therefore, the grating tilt angle α of the reflected VBG also needs to be smaller than a certain value to reflectively diffract the display light. In one example, the grating tilt angle α of the reflective VBG 1750 may be about 30°.

FIG. 17D is a diagram illustrating an example of a reflective VBG 1760 in a waveguide display, where light diffracted by the reflective VBG is not fully reflected and directed within the waveguide. The grating tilt angle α of the reflective VBG 1760 shown in FIG. 17D may be less than a certain value. As such, light coupled into the waveguide may strike the surface of the waveguide at an angle of incidence less than the critical angle, and thus be completely reflected and not guided within the waveguide. There is The grating tilt angle α of the reflective VBG 1760 may be less than about 30°. Therefore, the grating tilt angle α of the reflected VBG may also need to be larger than a certain value. As such, the grating tilt angle α of the reflected VBG is also within a certain range to reflectively diffract the display light into the waveguide such that the diffracted light can be guided by the waveguide through total internal reflection. There can be. Figures 17A-17D show that the grating tilt angle α can be smaller for reflective gratings than for transmission gratings.

によって決定され得、式中、λ_０は、ブラッグ条件を完璧に満たす光の波長であり、ｋ_ｏｕｔは、反射ＶＢＧ１８００によって回折される光の波動ベクトルである。反射ＶＢＧ１８００の格子傾斜角αが約３０°であるとき、反射ＶＢＧ１８００による光分散の量は、およそ、

であり得る。故に、角度分解能約２分を達成するために、反射ＶＢＧ１８００の厚さｄは、少なくとも約０．５ｍｍであり得る。 FIG. 18A illustrates light dispersion by an example reflective volume Bragg grating 1800 in a waveguide display, according to certain embodiments. Reflective VBG 1800 may be characterized by grating vector kg, thickness d, and average refractive index n. The surface normal direction of the reflective VBG 1800 is N. The amount of light dispersion due to the reflective VBG1800 is

where λ ₀ is the wavelength of light that perfectly satisfies the Bragg condition and k _out is the wave vector of the light diffracted by the reflected VBG 1800 . When the grating tilt angle α of the reflective VBG 1800 is approximately 30°, the amount of light dispersion due to the reflective VBG 1800 is approximately:

can be Therefore, to achieve an angular resolution of about 2 minutes, the thickness d of the reflective VBG 1800 can be at least about 0.5 mm.

によって決定され得、式中、λ_０は、ブラッグ条件を完璧に満たす光の波長であり、ｋ_ｏｕｔは、透過ＶＢＧ１８５０によって回折される光の波動ベクトルである。透過ＶＢＧ１８５０の格子傾斜角αが約６０°であるとき、透過ＶＢＧ１８５０による光分散の量は、およそ、

であり得る。故に、角度分解能約２分を達成するために、透過ＶＢＧ１８５０の厚さｄは、少なくとも約１．５ｍｍであり得、これは、同じ角度分解能を有する反射ＶＢＧの厚さの約３倍であり、達成が困難であり得るか、または著しい表示ヘイズを引き起こし得る。 FIG. 18B illustrates optical dispersion by an example transmissive volume Bragg grating 1850 in a waveguide display, according to certain embodiments. The transmissive VBG 1850 can similarly be characterized by grating vector kg, thickness d, and average refractive index n. The surface normal direction of the transparent VBG 1850 is N. The amount of light dispersion by the transmissive VBG1850 is

where λ ₀ is the wavelength of light that perfectly satisfies the Bragg condition and k _out is the wave vector of the light diffracted by the transmitted VBG 1850 . When the grating tilt angle α of the transmissive VBG 1850 is about 60°, the amount of light dispersion due to the transmissive VBG 1850 is approximately:

can be Thus, to achieve an angular resolution of about 2 minutes, the thickness d of the transmitted VBG 1850 can be at least about 1.5 mm, which is about 3 times the thickness of the reflected VBG with the same angular resolution, It can be difficult to achieve or can cause significant display haze.

Dispersion compensation may be desired in VBG-based waveguide displays to reduce their physical size, reduce VBG thickness and display haze, and achieve desired resolution. According to certain embodiments, one or more grating pairs (eg, transmission gratings) having matching grating vectors and operating in opposite diffraction conditions (eg, +1st order vs. −1st order diffraction) are can be used to compensate for the dispersion caused by

FIG. 19A is a front view of an example volume Bragg grating-based waveguide display 1900 with exit pupil expansion and dispersion reduction, in accordance with certain embodiments. FIG. 19B is a side view of an example volume Bragg grating-based waveguide display 1900 with exit pupil expansion and dispersion reduction, in accordance with certain embodiments. Waveguide display 1900 may be similar to waveguide display 1300 but may include input couplers different from input coupler 1320 . Waveguide display 1900 may include a substrate 1910 and first and second gratings 1930 and 1940 formed on or within substrate 1910 . The input coupler may include projector optics 1920 (eg, lenses) and an input grating 1922 rather than a prism. The display light may be collimated by projector optics 1920 and projected onto an input grating 1922, which collimates the display light into substrate 1910 by diffraction, for example, as described above with respect to FIGS. can be coupled to The display light may reach a first portion 1932 of the first grating 1930, be diffracted by the first portion 1932 of the first grating 1930, change its propagation direction, and reach another portion of the first grating 1930. Each of these other portions can reach and diffract the display light towards the second grating 1940 . A second grating 1940 may diffract display light out of substrate 1910 at different locations to form multiple exit pupils, as described above.

Each of the first portion 1932 and the other portions of the first grating 1930 have matching grating vectors (eg, have the same grating vector in the xy plane and the same and/or opposite grating vectors in the z direction). grating vectors, but recorded with different exposure durations to achieve different diffraction efficiencies). Therefore, they are induced by each other due to the opposite Bragg conditions of diffraction (eg, +1st and −1st orders of diffraction) in each of the first portion 1932 and the other portion of the first grating 1930 . Light dispersion can be compensated to reduce overall dispersion in one direction. Additionally, the input grating 1922 and the second grating 1940 have matching grating vectors (eg, have the same grating vectors in the xy plane and the same and/or opposite grating vectors in the z direction, but different grating vectors). (recorded with different exposure durations to achieve diffraction efficiency), and input grating 1922 may couple display light into substrate 1910, while second grating 1940 directs display light. can be coupled out from the wave path. Therefore, input grating 1922 and second grating 1940 are: Dispersion of display light caused by each other may be compensated to reduce overall dispersion in at least one direction. In this manner, the overall dispersion due to each of the first portion 1932 and other portions of the first grating 1930 can be reduced or canceled, and the overall dispersion due to the input grating 1922 and the second grating 1940 can also be , can be reduced or canceled. Therefore, the overall dispersion of display light by waveguide display 1900 can be minimized in any direction. As such, higher resolution of the displayed image can be achieved. Therefore, thin reflective or transmissive VBGs can be used as input and output couplers and still achieve the desired resolution. A transmissive VBG may also allow the first and second gratings to be at least partially overlapped to reduce the physical dimensions of the waveguide display as described above.

Waveguide display 1900 may include multiple polymer layers on one or more waveguide plates, with input grating 1922, first grating 1930, and second grating 1940 each recorded on multiple polymer layers. can be divided into multiple lattices. Gratings on each polymer layer can cover a different respective FOV and optical spectrum, and a combination of multiple polymer layers can provide full FOV and spectral coverage. In this manner, each polymer layer can be thin (eg, about 20 μm to about 100 μm) and can be exposed fewer times (eg, less than about 100) to record fewer gratings to reduce haze; The overall efficiency of multiple polymer layers can still be high for the entire FOV and spectrum. In the example shown in FIGS. 19A and 19B, waveguide display 1900 may include first polymer layer 1912 and second polymer layer 1914 on one or more plates or substrates. Each polymer layer 1912 or 1914 may include portions of input grating 1922 , first grating 1930 , and/or second grating 1940 .

FIG. 20A illustrates another example volume Bragg grating-based waveguide display 2000 with exit pupil enlargement, dispersion reduction, form factor reduction, and efficiency improvement, according to certain embodiments. Like waveguide display 2000 , waveguide display 2000 may include substrate 2010 , which may be similar to substrate 1910 . Substrate 2010 can include a first surface 2012 and a second surface 2014 . Display light from a light source (eg, an LED) can be coupled into the substrate 2010 by an input coupler 2020, and total internal reflection such that the display light can propagate within the substrate 2010 (eg, in the −y direction). can be reflected by first surface 2012 and second surface 2014 through . As explained above, input coupler 2020 may include a diffractive coupler, such as a multiplexed VBG, which may couple different colors of display light at different diffraction angles into substrate 2010 .

Waveguide display 2000 may include first grating 2030 and second grating 2040 formed on first surface 2012 and/or second surface 2014 . Waveguide display 2000 may also include third grating 2060 and fourth grating 2070 formed in first surface 2012 and/or second surface 2014 . The third lattice 2060 and the fourth lattice 2070 may each be multiplexed VBGs containing multiple VBGs. In some embodiments, the third grating 2060, the fourth grating 2070, and the first grating 2030 can be on the same surface of the substrate 2010 or different surfaces. In some embodiments, the third grating 2060, the fourth grating 2070, and the first grating 2030 may be in the same grating or different regions of the same grating material layer.

In some embodiments, first grid 2030, third grid 2060, and fourth grid 2070 may each include multiple VBGs. Third grating 2060 and first grating 2030 may be such that each VBG in third grating 2060 may match a respective VBG in first grating 2030 (eg, have the same grating vector in the xy plane). and have the same and/or opposite grating vectors in the z-direction) can be recorded in multiple exposures and under similar recording conditions (however, different exposure durations are used to achieve different diffraction efficiencies). can be recorded over a period of time). For example, in some embodiments, the VBG in the third grating 2060 and the corresponding VBG in the first grating 2030 have the same grating period and the same grating tilt angle (and hence the same grating vector), and the same thickness. can have Fourth grating 2070 and first grating 2030 may be such that each VBG in fourth grating 2070 may match a respective VBG in first grating 2030 (eg, have the same grating vector in the xy plane). and have the same and/or opposite grating vectors in the z direction) in multiple exposures and under similar recording conditions (but over different exposure durations). In some embodiments, the recording conditions for recording the third grating 2060 are different because the third grating 2060 and the fourth grating 2070 may have different Bragg conditions (and different grating vectors). The recording conditions for recording the fourth grating 2070 may differ so as to diffract light from the FOV range and/or wavelength range to improve the overall diffraction efficiency of visible light within the large FOV range. . In some embodiments, the third grating 2060 and the fourth grating 2070 may have similar grating vectors, thus allowing light from the same FOV range and/or wavelength range to pass with similar or different diffraction efficiencies. Diffraction may improve the overall diffraction efficiency of light within a particular FOV range and/or wavelength range.

In some embodiments, VBGs in the first lattice 2030 that match VBGs in the third lattice 2060 may be recorded in one area (eg, upper area) of the first lattice 2030, Other VBGs in first grid 2030 that match VBGs in grid 2070 of 4 may be recorded in different areas (eg, lower regions) of first grid 2030 . In one example, the third grating 2060 and the fourth grating 2070 can each have a thickness of about 20 μm and can each contain about 20 VBGs recorded over about 20 exposures. In an example, the first grating 2030 can have a thickness of about 20 μm or greater and can include about 40 VBGs recorded in different areas over about 40 exposures. The second grating 2040 can have a thickness of about 20 μm or greater and can include about 50 VBGs recorded over about 50 exposures.

Input coupler 2020 may couple display light from the light source into substrate 2010 . The display light may reach the third grating 2060 directly or may be reflected by the first surface 2012 and/or the second surface 2014 to the third grating 2060, the size of the display light beam being determined by the input coupler It can be slightly larger than the size in 2020. Each VBG in the third grating 2060 can diffract a portion of the display light within the FOV range and wavelength range that approximately satisfies the VBG's Bragg condition to the upper region of the first grating 2030 . As explained above, the upper region of first grid 2030 may include VBGs that match the VBGs in third grid 2060 . Thus, display light diffracted by the VBG in third grating 2060 propagates through substrate 2010 (eg, along the direction indicated by lines 2032) through total internal reflection, while a portion of the display light is Each time display light propagating in 2010 reaches first grating 2030 , it may be diffracted by a corresponding VBG in first grating 2030 to second grating 2040 .

Display light that is not diffracted by the third grating 2060 (eg, due to diffraction efficiency less than 100%, or due to the small FOV range and/or wavelength range near the Bragg condition) propagates within the substrate 2010. One can continue and reach the fourth grid 2070 . Each VBG in the fourth grating 2070 may diffract a portion of the display light within the FOV range and wavelength range that approximately satisfies the VBG's Bragg condition to the region below the first grating 2030 . As explained above, the area below the first grid 2030 may include VBGs that match the VBGs in the fourth grid 2070 . Thus, display light diffracted by the VBG in fourth grating 2070 propagates through substrate 2010 (eg, along the direction indicated by lines 2034) through total internal reflection, while a portion of the display light is Each time display light propagating in 2010 reaches first grating 2030 , it may be diffracted by a corresponding VBG in first grating 2030 to second grating 2040 . The second grating 2040 directs a portion of the display light propagating in the substrate 2010 to an eyebox 2050 (eg, from the second grating 2040 in the +z or −z direction) each time the display light reaches the second grating 2040 . at a distance of about 18 mm), the display light from the first grating 2030 may be magnified in different directions (eg, approximately in the y-direction). In this manner, display light can be expanded in two dimensions to fill the eyebox 2050 .

FIG. 20B illustrates a replicated exit pupil in an eyebox 2080 (eg, eyebox 2050) of a volume Bragg grating-based waveguide display 2000. FIG. The exit pupils may include a first set of exit pupils 2082 replicated by gratings 2060 , 2030 and 2040 and a second set of exit pupils 2084 replicated by gratings 2070 , 2030 and 2040 . In embodiments in which gratings 2060 and 2070 have different grating vectors, the first set of exit pupils 2082 and the second set of exit pupils 2084 may correspond to different FOV ranges and/or different wavelength ranges. In embodiments where gratings 2060 and 2070 have similar grating vectors, the first set of exit pupils 2082 and the second set of exit pupils 2084 may correspond to the same FOV range and/or wavelength range. The first set of exit pupils 2082 and the second set of exit pupils 2084 may overlap or partially overlap. Thus, the pupil replication density can be increased and the light can be more uniform within the eyebox due to the diffraction of the display light by the two spatially multiplexed VBG sets.

Additionally, dispersion can be reduced in two dimensions due to double diffraction in each dimension by a pair of matched gratings operating under opposite Bragg conditions as described above. Furthermore, display light in a wider bandwidth can be diffracted with higher diffraction efficiency by the grating into the eyebox because of the lower number of exposures (and thus the higher refractive index modulation Δn of each VBG). Hence, the power efficiency of waveguide displays can be improved. In some embodiments, first grating 2030 and second grating 2040 may at least partially overlap to reduce the form factor of waveguide display 2000 as described above.

FIG. 21A illustrates another example volume Bragg grating-based waveguide display 2100 with exit pupil enlargement, dispersion reduction, and form factor reduction, according to certain embodiments. Like waveguide display 2100 , waveguide display 2100 can include substrate 2110 , which can be similar to substrate 2110 . Substrate 2110 can include a first surface 2112 and a second surface 2114 . Display light from a light source (eg, an LED) can be coupled into the substrate 2110 by an input coupler 2120 and can propagate through the substrate 2110 through total internal reflection at the first surface 2112 and the first surface 2112 so that the display light can propagate within the substrate 2110 . can be reflected by two surfaces 2114 . As described above, input coupler 2120 may include a diffractive coupler such as a VBG. Waveguide display 2100 may also include first grating 2130 and second grating 2140 formed in first surface 2112 and/or second surface 2114 . In the example shown in FIG. 21A , the first grating 2130 and the second grating 2140 may be at different locations in the x-direction and may overlap in at least a portion of the see-through area of waveguide display 2100 . A first grating 2130 and a second grating 2140 are configured to direct an incident display light beam to fill an eyebox 2150 (eg, at a distance of about 18 mm from second grating 2140 in the +z or -z direction) with display light. can be used for biaxial pupil expansion to expand in two dimensions. For example, the first grating 2130 may expand the display light beam approximately in the y-direction, while the second grating 2140 may expand the display light beam approximately in the x-direction.

Additionally, waveguide display 2100 may include a third grating 2160 formed in first surface 2112 and/or second surface 2114 . In some embodiments, the third grating 2160 and the first grating 2130 can be placed on the same surface of the substrate 2110 but at different locations in the y-direction. In some embodiments, the third grating 2160 and the first grating 2130 may be in the same grating or different regions of the same grating material layer. In some embodiments, third grating 2160 may be spatially separated from first grating 2130 . In some embodiments, third grid 2160 and first grid 2130 may match each VBG in third grid 2160 with each VBG in first grid 2130 (eg, xy with the same grating vector in the plane and the same and/or opposite grating vector in the z-direction), in the same number of exposures, and under similar recording conditions (however, different diffraction efficiencies can be recorded over different exposure durations to achieve).

Input coupler 2120 may couple display light from the light source into substrate 2110 . The display light may propagate in the substrate 2110 approximately along the x-direction and may reach the third grating 2160 directly or may reach the third grating 2160 by the first surface 2112 and/or the second surface 2114. can be reflected to Each VBG in the third grating 2160 may diffract a portion of the display light down to the first grating 2130 within the FOV range and wavelength range that approximately satisfies the VBG's Bragg condition. Display light diffracted by the VBG in the third grating 2160 propagates along a direction (eg, approximately in the y-direction indicated by line 2132) within the substrate 2110 through total internal reflection, whereas the display light A portion may be diffracted to the second grating 2140 by the corresponding VBG in the first grating 2130 each time the display light propagating in the substrate 2110 reaches the first grating 2130 . Second grating 2140 then captures the display light from first grating 2130 by diffracting a portion of the display light propagating in substrate 2110 into eyebox 2150 each time it reaches second grating 2140 . The light can be expanded in different directions (eg, approximately in the x-direction). Input coupler 2120 and second grating 2140 have a matching VBG (e.g., same grating vector in the xy plane, z-direction VBG) with the same or opposite lattice vectors in . Similarly, gratings 2130 and 2160 have matching VBGs (eg, have the same grating vector in the xy plane and the same and/or or VBG) with opposite lattice vectors. Thus, the overall dispersion due to gratings in waveguide display 2100 can be reduced or minimized.

Each of the first grating 2130 and the second grating 2140 may, for example, have a thickness of less than 100 μm (eg, 20 μm) and may include, for example, less than 50 VBGs. Therefore, any area within the optical see-through region of waveguide display 2100 may contain less than 100 VBGs. Therefore, display haze may not increase. Additionally, the first grating 2130 and the second grating 2140 may at least partially overlap to reduce the form factor of the waveguide display 2100 so that the physical dimensions of the waveguide display 2100 are similar to those of ordinary eyeglasses. can be similar to the physical dimensions of the lens of

FIG. 21B illustrates an example volume Bragg grating-based waveguide display 2105 with exit pupil enlargement, dispersion reduction, form factor reduction, and efficiency improvement, according to certain embodiments. Like waveguide display 2100, waveguide display 2105 includes a first grating 2135, a second grating 2145, a third grating formed on first surface 2116 and/or second surface 2118 of substrate 2115. 2165, and a fourth grating 2175. First lattice 2135, second lattice 2145, third lattice 2165, and fourth lattice 2175 may each include multiplexed VBGs that include multiple VBGs. In some embodiments, third grating 2165 , fourth grating 2175 and first grating 2135 may be on the same surface of substrate 2115 . In some embodiments, the third grating 2165, the fourth grating 2175, and the first grating 2135 may be in the same grating or different regions of the same grating material layer.

Each VBG in the third grating 2165 has a grating vector that matches the grating vector of the respective VBG in the first grating 2135 (eg, has the same grating vector in the xy plane and the same and/or or with opposite lattice vectors). Each VBG in the fourth grating 2175 has a grating vector that matches the grating vector of the respective VBG in the first grating 2135 (eg, has the same grating vector in the xy plane and the same and/or or with opposite lattice vectors). In some embodiments, the third grating 2165 and the fourth grating 2175 can have different grating vectors, thus diffracting light from different FOV ranges and/or wavelength ranges to produce light within a large FOV range. can improve the overall diffraction efficiency of visible light. In some embodiments, the third grating 2165 and the fourth grating 2175 may have similar grating vectors, thus allowing light from the same FOV range and/or wavelength range to pass with similar or different diffraction efficiencies. Diffraction may improve the overall diffraction efficiency of light within a particular FOV range and/or wavelength range.

Input coupler 2125 may couple display light from the light source into substrate 2115 . The display light may reach third grating 2165 directly or may be reflected to third grating 2165 by first surface 2116 and/or second surface 2118 . Each VBG in the third grating 2165 can diffract a portion of the display light within the FOV range and wavelength range that approximately satisfies the VBG's Bragg condition to the left region of the first grating 2135 . Display light diffracted by the VBG in third grating 2165 propagates through substrate 2115 (eg, along the direction indicated by line 2136) through total internal reflection, while a portion of the display light is Each time display light propagating through reaches the first grating 2135 , it may be diffracted by the corresponding VBG in the first grating 2135 to the second grating 2145 .

Display light not diffracted by third grating 2165 (eg, due to diffraction efficiency less than 100%, or due to small FOV range and/or wavelength range near Bragg condition) propagates within substrate 2115. One can continue and reach the fourth grating 2175 . Each VBG in fourth grating 2175 may diffract a portion of the display light within the FOV range and wavelength range that approximately satisfies the VBG's Bragg condition to the right region of first grating 2135 . Display light diffracted by the VBG in fourth grating 2175 propagates through substrate 2115 (e.g., along the direction indicated by line 2138) through total internal reflection, while a portion of the display light is Each time display light propagating through reaches the first grating 2135 , it may be diffracted by the corresponding VBG in the first grating 2135 to the second grating 2145 .

The second grating 2145 directs a portion of the display light propagating in the substrate 2115 each time it reaches the second grating 2145 to an eyebox 2155 (e.g., approximately 18 mm distance) may magnify the display light from the first grating 2135 in different directions (eg, approximately in the x-direction). In this way the display light can be expanded in two dimensions to fill the eyebox 2155 . The resulting exit pupils may include a first set of exit pupils replicated by gratings 2165 , 2135 and 2145 and a second set of exit pupils replicated by gratings 2175 , 2135 and 2145 . In embodiments where gratings 2165 and 2175 have different grating vectors, the first set of exit pupils and the second set of exit pupils may correspond to different FOV ranges and/or different wavelength ranges. In embodiments where gratings 2165 and 2175 have similar grating vectors, the first set of exit pupils and the second set of exit pupils may correspond to the same FOV range and/or wavelength range. The first set of exit pupils and the second set of exit pupils may overlap or partially overlap. Thus, the pupil replication density can be increased and the light can be more uniform within the eyebox due to the diffraction of the display light by the two spatially multiplexed VBG sets.

In some embodiments, the full FOV range of the displayed image may be divided into two or more FOV ranges to be covered by two or more sets of grids. Two or more FOV ranges can be glued together to provide a full field of view. For each FOV range, a set of gratings can be used to expand the exit pupil in two dimensions to fill the eyebox.

FIG. 22A is a front view of an example volume Bragg grating-based waveguide display 2200 including two image projectors 2220 and 2250, in accordance with certain embodiments. FIG. 22B is a side view of an example volume Bragg grating-based waveguide display 2200 including two image projectors 2220 and 2250, in accordance with certain embodiments. Image projector 2220, first input grating 2222, first upper grating 2230, and lower grating 2240 may be used to provide a first portion (eg, left half) of the total FOV of waveguide display 2200. . Display light in a first portion of the full FOV may be collimated and projected onto a first input grating 2222, which may be, for example, as described above with respect to FIGS. Display light may be coupled into waveguide 2210 by diffraction. The display light may reach the first portion 2232 of the first upper grating 2230 , be diffracted by the first portion 2232 of the first upper grating 2230 to change the direction of , and each of the other portions can diffract the display light toward the lower grating 2240 . Lower grating 2240 may diffract display light out of waveguide 2210 at different locations to form multiple exit pupils as described above. Each of the first portion 2232 of the first upper grating 2230 and the other portion of the first upper grating 2230 may have similar grating parameters (but may have different exposure durations to achieve different diffraction efficiencies). ). Therefore, they result from opposite Bragg conditions for diffraction (eg, +1st and −1st orders of diffraction) in each of the first portion 2232 of the first upper grating 2230 and the other portion of the first upper grating 2230. can compensate for the dispersion of the display light caused by each other and reduce the overall dispersion.

Additionally, first input grating 2222 and lower grating 2240 may have similar grating parameters or similar grating vectors at least in the xy plane (however, at different exposure durations to achieve different diffraction efficiencies). can be recorded), a first input grating 2222 may couple display light into waveguide 2210 , while a lower grating 2240 may couple display light out of waveguide 2210 . Thus, the first input grating 2222 and the lower grating 2240 are induced by each other due to opposite diffraction directions and opposite Bragg conditions for their respective diffractions (eg, +1st and −1st orders of diffraction). can be compensated for to reduce the overall dispersion. In this manner, the dispersion due to each of the first portion 2232 of the first upper grating 2230 and the other portion of the first upper grating 2230 can be canceled, as well as the dispersion due to the first input grating 2222 and the lower grating 2240. It can also be canceled out.

Similarly, image projector 2250, second input grating 2252, second upper grating 2260, and lower grating 2240 (or a different lower grating) are arranged in different portions (e.g., right half) of the total FOV of waveguide display 2200. can be used to provide As explained above, lower grating 2240 may be used for both portions of the field of view or may include two gratings, one for each portion of the field of view. The dispersion due to each of the first portion 2262 and other portions of the second upper grating 2260 can be canceled, and the dispersion due to the second input grating 2252 and the lower grating 2240 can also be canceled. Therefore, the overall dispersion of display light by waveguide display 2200 can be minimized in any direction. As such, higher resolution of the displayed image can be achieved even though the polymer layer is thin and the transmitted VBG is recorded in the thin polymer layer.

Waveguide display 2200 may include multiple polymer layers on one or more waveguide plates, such as first waveguide plate 2212 and second waveguide plate 2214 . Input gratings 2222 and 2252, upper gratings 2230 and 2260, and lower grating 2240 can each be divided into multiple gratings recorded in multiple polymer layers. The gratings on each polymer layer can cover different respective FOVs and optical spectra. Combinations of multiple polymer layers can provide full FOV and spectral coverage. In this manner, each polymer layer can be thin (eg, about 20 μm to about 100 μm) and can be exposed fewer times (eg, less than about 100) to record fewer gratings, thus reducing fogging of see-through images. Reduce. The overall efficiency of multiple polymer layers can still be high for the entire FOV and visible light spectrum.

FIG. 23A is a front view of an example volume Bragg grating-based waveguide display 2300 including a single image projector 2320 and a grating for field stitching, according to certain embodiments. FIG. 23B is a side view of an example volume Bragg grating-based waveguide display 2300 with gratings for image projector 2320 and field stitching, according to certain embodiments. Waveguide display 2300 may include multiple polymer layers on one or more waveguide plates 2310 . Image projector 2320 , input grating 2330 , upper grating 2340 , and lower grating 2350 may be used to provide a first portion (eg, left half) of the total FOV of waveguide display 2300 . As described above, the display light in the first portion of the FOV may be collimated and projected onto an input grating 2330, which refracts the display light, for example, by diffraction as described above. can be coupled into waveguide plate 2310 . The display light may reach a first portion of the upper grating 2340 and may be diffracted by the first portion of the upper grating 2340 to other portions of the upper grating 2340, each of which directs the display light to the lower grating. can be diffracted towards 2350. The bottom grating 2350 may diffract the display light out of the waveguide plate 2310 at different locations to replicate the exit pupil as described above. Each of the first and other portions of upper grating 2340 may compensate for dispersion caused by each other, and input grating 2330 and lower grating 2350 may also compensate for dispersion caused by each other as described above. can.

Image projector 2320 , input grating 2332 , upper grating 2342 , and lower grating 2352 may be used to provide a portion (eg, right half) of the total FOV of waveguide display 2300 . Display light may be collimated and coupled into waveguide plate 2310 by input grating 2332 . The display light may reach a first portion of the upper grating 2342 and may be diffracted by the first portion of the upper grating 2342 to other portions of the upper grating 2342, which each transmit the display light to the lower grating. 2352 can be diffracted. The lower grating 2352 may diffract the display light out of the waveguide plate 2310 at different locations to replicate the exit pupil as described above. Each of the first and other portions of upper grating 2342 may compensate for dispersion caused by each other, and input grating 2332 and lower grating 2352 may also compensate for dispersion caused by each other as described above. can.

Waveguide display 2300 may include multiple polymer layers on one or more waveguide plates 2310, with input gratings 2330 and 2332, upper gratings 2340 and 2342, and lower gratings 2350 and 2352 each comprising multiple polymer layers. , and the gratings on each polymer layer can cover different respective FOVs and optical spectra. Combinations of multiple polymer layers can provide full FOV and spectral coverage. In this manner, each polymer layer can be thin (eg, about 20 μm to about 100 μm) and can be exposed fewer times (eg, less than about 100) to record fewer gratings to reduce haze; The overall efficiency of multiple polymer layers can still be high for the entire FOV and visible light spectrum.

In the example shown in FIG. 23B, each of input grating 2330, top grating 2340, and bottom grating 2350 can be split into two multiplexed gratings, each recorded in a respective polymer layer, Also, multiple VBGs, each covering a respective FOV, can be recorded in each respective polymer layer to form a multiplexed grating. Similarly, each of input grating 2332, upper grating 2342, and lower grating 2352 can be split into two multiplexed gratings, each recorded in a respective polymer layer, and each Covering the FOV, multiple VBGs can each be recorded on their respective polymer layers to form a multiplexed grating. As shown in FIG. 23B, input gratings 2332 and 2330 may be in different polymer layers. Similarly, the top grids 2340 and 2342 can be in different polymer layers and the bottom grids 2350 and 2352 can be in different polymer layers. Therefore, crosstalk between them can be reduced.

FIG. 24 illustrates an example volume Bragg grating-based waveguide display 2400 including multiple grating layers for different fields of view and/or light wavelengths, in accordance with certain embodiments. VBG-based waveguide display 2400 may be an example of VBG-based waveguide display 2300 described above. In waveguide display 2400, gratings can be spatially multiplexed along the z-direction. For example, waveguide display 2400 may include multiple substrates, such as substrates 2410, 2412, 2414, and the like. The substrates may contain the same material(s) with similar refractive indices. One or more VBGs (eg, VBGs 2420, 2422, 2424, etc.) may be fabricated on each substrate, such as recorded in a layer of holographic material formed on the substrate. The VBG may be a reflective or transmissive grating. Substrates with VBG can be arranged in a substrate stack along the z-direction for spatial multiplexing. Each VBG includes multiple gratings designed for different Bragg conditions for coupling display light in different wavelength ranges and/or different FOVs into or out of the waveguide. It may be multiplexed VBG.

In the example shown in FIG. 24, VBG 2420 may couple light 2434 from the positive field of view into the waveguide as indicated by ray 2444 within the waveguide. VBG 2422 may couple light 2430 from about 0° field of view into the waveguide, as shown by ray 2440 in the waveguide. VBG 2424 may couple light 2432 from the negative field of view into the waveguide as shown by ray 2442 in the waveguide. As explained above, each of the VBGs 2420, 2422, and 2424 may be multiplexed VBGs with many exposures, thus allowing light from different FOV ranges to be coupled into the waveguides. or can be coupled out from the waveguide.

FIG. 25 illustrates the fields of view of multiple gratings in an example volume Bragg grating-based waveguide display, in accordance with certain embodiments. In some embodiments, each grating may be in a respective grating layer or on a respective waveguide plate. Each of the gratings may be a multiplexed grating containing many exposures, allowing display light from multiple FOV ranges to be coupled into or out of the waveguide with high efficiency. obtain. For example, curve 2510 may show the diffraction efficiency of a first VBG (eg, VBG 2422 in FIG. 24) for light from different fields of view. Curve 2520 may show the diffraction efficiency of a second VBG (eg, VBG 2420 of FIG. 24) for light from different fields of view. Curve 2530 may show the diffraction efficiency of a third VBG (eg, VBG 2424 in FIG. 24) for light from different fields of view. The first, second, and third VBGs, when arranged in a stack, can more uniformly diffract light within a full field of view (eg, from about -20° to about 20°) with high efficiency. In some embodiments, a first VBG, a second VBG, and a third VBG may be used to couple display light of the same color. Different VBG sets can be used to cover the entire field of view for different colors of display light.

A VBG designed to diffract light within one wavelength and from one angular range may also diffract light within another wavelength and from another angular range. For example, a VBG characterized by a particular period and tilt angle can diffract light within different wavelengths and from different angles of incidence.

FIG. 26A illustrates diffraction of different colors of light from corresponding fields of view by an example volume Bragg grating 2610 . As shown in the example, VBG 2610 may diffract blue light 2602 from a first angle of incidence into the waveguide at a first diffraction angle. VBG 2610 may also diffract green light 2604 from a second angle of incidence into the waveguide at a second diffraction angle. VBG 2610 may also diffract red light 2606 from a third angle of incidence into the waveguide at a third diffraction angle.

FIG. 26B illustrates the relationship between the grating period of a volume Bragg grating and the corresponding field of view for incident light of different colors. Curve 2620 shows that red light from different fields of view can be diffracted by VBGs with different grating periods. Similarly, curve 2630 shows that green light from different fields of view can be diffracted by VBGs with different grating periods, and curve 2630 shows that blue light from different fields of view can be diffracted by VBGs with different grating periods. Show that you get FIG. 26B also shows that a VBG with a particular grating period and tilt angle can diffract light within different wavelengths and from different angles of incidence (eg, from different fields of view). Region 2605 of FIG. 26B shows a grating capable of diffracting more than one color of light from more than one respective FOV. For example, dashed line 2650 in FIG. 26B may correspond to a VBG having a grating period of about 450 nm, which diffracts red light from about a −7° field of view, diffracts green light from about a 2° field of view, It can diffract blue light from about a 6° field of view.

As explained above, the VBG may be a reflective VBG or a transmissive VBG. A reflected VBG and a transmitted VBG may have different diffraction properties. For example, as described above with respect to FIGS. 18A and 18B, reflective gratings may have relatively lower dispersion than transmission gratings of similar thickness. Although transmission gratings used as output gratings may allow grating overlap for two-dimensional exit pupil replication to reduce the physical size of the waveguide display, as described above with respect to FIG. , the reflective grating may not be, as described above with respect to FIG.

FIG. 27A illustrates the diffraction efficiency of an example transmissive volume Bragg grating with the same thickness but different refractive index modulations. Diffraction efficiency can be polarization dependent. Curve 2710 shows the diffraction efficiency of an example transmitted VBG for s-polarized light, while curve 2720 shows the diffraction efficiency of an example transmitted VBG for p-polarized light. Curve 2730 shows the average diffraction efficiency of an example transmitted VBG for s-polarized light and p-polarized light (eg, unpolarized light). As shown in FIG. 27A, curves 2710 and 2720 may correspond to functions proportional to the square of the sinusoidal function (eg, ∝ sin ² (a×n1×D)). The diffraction efficiency of a transmission grating can increase or decrease with increasing refractive index modulation. Therefore, increasing the refractive index modulation of the transmitted VBG may not necessarily increase the diffraction efficiency of the transmitted VBG.

FIG. 27B illustrates the diffraction efficiency of an example reflective volume Bragg grating with the same thickness but different refractive index modulations. The diffraction efficiency of the reflected VBG is also polarization dependent. Curve 2760 shows the diffraction efficiency of an example reflected VBG for s-polarized light, while curve 2720 shows the diffraction efficiency of an example reflected VBG for p-polarized light. Curve 2730 shows the average diffraction efficiency of an example reflected VBG for s-polarized light and p-polarized light (eg, unpolarized light). As shown in FIG. 27B, the diffraction efficiency of the reflected VBG can increase with increasing refractive index modulation (eg, ∝ tanh ² (a×n1×D)) until the refractive index modulation reaches a certain value. can saturate when

Figures 28A-28D illustrate the diffraction efficiency of an example transmissive volume Bragg grating with different refractive index modulations as a function of the angle of incidence deviation from the Bragg condition. Curve 2810 in FIG. 28A shows the diffraction efficiency of an example transmitted VBG with a refractive index modulation of about 0.002, with the peak diffraction efficiency of the main lobe approaching 100%. Curve 2820 of FIG. 28B shows the diffraction efficiency of an example of a transmitted VBG with a refractive index modulation of about 0.004, compared to the transmitted VBG of FIG. Diffraction efficiency curve 2820 has two peaks and increased sidelobes. Curve 2830 of FIG. 28C shows the diffraction efficiency of an example transmitted VBG with a refractive index modulation of about 0.0054, compared to the transmitted VBG of FIG. can increase. Curve 2840 of FIG. 28D shows the diffraction efficiency of an example of a transmitted VBG with a refractive index modulation of about 0.0078, compared to the transmitted VBG of FIG. It has a peak and the sidelobes increase.

Figures 29A-29D illustrate the diffraction efficiency of example reflective volume Bragg gratings with different refractive index modulations as a function of the angle of incidence deviation from the Bragg condition. Curve 2910 in FIG. 29A shows the diffraction efficiency of an example reflected VBG with a refractive index modulation of about 0.002, with a mainlobe peak diffraction efficiency greater than 80%. Curve 2920 of FIG. 29B shows the diffraction efficiency of an example of a reflected VBG with a refractive index modulation of about 0.004, compared to the reflected VBG of FIG. The angular range increases and the sidelobes increase. Curve 2930 of FIG. 29C shows the diffraction efficiency of an example over-reflected VBG with a refractive index modulation of about 0.0054, compared to the reflected VBG of FIG. The FWHM angular range is further increased and the sidelobes are further increased as well. Curve 2940 of FIG. 29D shows the diffraction efficiency of an example reflected VBG with a refractive index modulation of about 0.0078, compared to the reflected VBG of FIG. The angular range is further increased and the sidelobes are further increased as well.

For a transmissive VBG, the diffraction efficiency of polarized light can be a function of the refractive index modulation (eg, ∝ sin ² (a×n1×D)), as shown in FIG. 27A. Additionally, the diffraction efficiency can be color dependent. For example, a transmissive VBG requires a lower refractive index modulation to reach the first diffraction peak shown in FIG. 27A for one color (e.g. blue) than another color (e.g. green or red). obtain. A grating with a particular refractive index modulation lower than that corresponding to the first diffraction peak shown in FIG. 27A may have a higher diffraction efficiency for blue light than for green or red light.

30A-30C illustrate the diffraction efficiency of an example transmissive VBG with a first refractive index modulation (eg, about 0.01). A transmissive VBG may diffract different colors of light from different respective fields of view with different respective diffraction efficiencies, as described above with respect to FIGS. 26A and 26B. For example, curve 3010 in FIG. 30A may illustrate the diffraction efficiency of a transmitted VBG for blue light from about a 14° field of view, with peak diffraction efficiency that may approach 100%. Curve 3020 of FIG. 30B may illustrate the diffraction efficiency of the same transmitted VBG for green light from a field of view of about 10°, where the peak diffraction efficiency has yet to reach 100% (eg, about 90%). Curve 3030 in FIG. 30C may illustrate the diffraction efficiency of the same transmitted VBG for red light from a field of view of about 3°, and the peak diffraction efficiency may be about 80%.

Figures 30D-30F illustrate the diffraction efficiency of an example transmissive VBG with a second refractive index modulation (eg, 0.012). The transmissive VBG may differ from the transmissive VBG associated with FIGS. 30A-30C only in refractive index modulation. A transmissive VBG may diffract different colors of light from different respective fields of view with different respective diffraction efficiencies. For example, curve 3012 in FIG. 30D may illustrate the diffraction efficiency of a transmitted VBG for blue light from a field of view of about 14°, where the peak diffraction efficiency is the first diffraction efficiency such that the refractive index modulation is shown in FIG. The greater than refractive index modulation associated with the peak may have decreased from the peak value of about 100% shown in FIG. 30A. Curve 3022 of FIG. 30E may illustrate the diffraction efficiency of the same transmitted VBG for green light from about a 10° field of view, where the peak diffraction efficiency may be increased (eg, greater than 90%). Curve 3032 of FIG. 30F may illustrate the diffraction efficiency of the same transmitted VBG for red light from about a 3° field of view, and the peak diffraction efficiency may be increased to over 80%.

30G-30I illustrate the diffraction efficiency of an example transmissive VBG with a third refractive index modulation (eg, 0.015). The transmissive VBG may differ from the transmissive VBG associated with FIGS. 30A-30F only in refractive index modulation. A transmissive VBG may diffract different colors of light from different respective fields of view with different respective diffraction efficiencies. For example, curve 3014 of FIG. 30G may illustrate the diffraction efficiency of a transmitted VBG for blue light from a field of view of approximately 14°, where the peak diffraction efficiency is the first diffraction efficiency such that the refractive index modulation is shown in FIG. It may further decrease from the values shown in FIG. 30D because it is larger than the refractive index modulation associated with the peak. Curve 3024 in FIG. 30H may illustrate the diffraction efficiency of the same transmitted VBG for green light from about a 10° field of view, and the peak diffraction efficiency may also decrease from its maximum. Curve 3034 of FIG. 30I may illustrate the diffraction efficiency of the same transmitted VBG for red light from about a 3° field of view, and the peak diffraction efficiency may be further increased.

In contrast, for a reflective VBG, the diffraction efficiency may not decrease with increasing refractive index modulation, as shown in Figures 27B and 29A-29D. The FWHM angular range of the main lobe and side lobes of the diffraction efficiency curve can increase with increasing refractive index modulation.

FIG. 31A illustrates the minimum refractive index modulation of transmissive volume Bragg gratings with different grating periods to achieve diffraction saturation for different colors. Curve 3110 shows the minimum refractive index modulation of transmitted VBG to achieve maximum diffraction efficiency for red light, while curve 3120 shows the minimum refractive index modulation of transmitted VBG to achieve maximum diffraction efficiency for green light. , curve 3130 shows the minimum refractive index modulation of the transmitted VBG to achieve maximum diffraction efficiency for blue light. As illustrated, for a grating with a given grating period and thickness, the minimum refractive index modulation to achieve maximum diffraction efficiency can be different for different colors. For example, the minimum refractive index modulation for maximum diffraction efficiency for blue light may be lower than for green or red light. Therefore, for gratings that can diffract light in multiple colors, as also illustrated in FIGS. At some point, the diffraction efficiency of the same grating for green and red light may be lower, and when the refractive index modulation is at a value that can achieve the highest diffraction efficiency for red light, blue and green light The diffraction efficiencies of the same gratings for can decrease from their peak values. Therefore, there may need to be some trade-off between diffraction efficiencies for different colors.

FIG. 31B illustrates a curve 3140 showing refractive index modulation for transmission gratings with different grating periods to avoid refractive index modulation saturation of any color. For example, for a grating capable of diffracting blue light, the refractive index modulation can be determined based on the refractive index modulation saturation of blue light. For gratings that can only diffract green and red light, the refractive index modulation can be determined based on the refractive index modulation saturation of green light. For gratings that can only diffract red light, the refractive index modulation can be determined based on the refractive index modulation saturation of red light.

As explained above, to cover the entire field of view for red, green, and blue light, the VBG may be a multiplexed grating exposed multiple times to different recording light patterns, each exposure can record gratings that can diffract red, green, and blue light from different respective fields of view. Gratings in a multiplexed VBG can have different grating periods. A multiplexed VBG can be used to diffract all colors of light from the full field of view. Additionally, the gratings in the multiplexed VBG can have different refractive index modulations to optimize the diffraction efficiency for different colors.

FIG. 31C is a diagram 3150 illustrating an example grating layer including multiplexed VBGs of different pitches and different refractive index modulations for optimized diffraction efficiency and diffraction efficiency uniformity, according to certain embodiments. Each data point 3152 in diagram 3150 indicates a grating period and corresponding refractive index modulation. In the illustrated example, the grating layer can include more than 40 gratings. The grating layer can have a maximum refractive index modulation of about 0.08. Each grating may have a refractive index modulation of about 0.002 or less. Multiplexed gratings can be combined to provide a full FOV for visible light.

It may generally be desirable to multiplex more gratings in a multiplexed VBG to increase the diffraction efficiency of light for large fields of view. However, when many gratings are multiplexed in a multiplexed VBG, crosstalk can occur between gratings.

FIG. 32A illustrates crosstalk induced by an example of multiplexed volume Bragg gratings in a waveguide display 3200. FIG. Waveguide display 3200 may include multiplexed input gratings, including input grating 3212 . Waveguide display 3200 also includes a multiplexed output grating 3210 that includes two or more output gratings, such as a first output grating 3214 and a second output grating 3216, which may be recorded in the same grating layer or multiple grating layers. obtain. Display light, in a first color and for a first field of view, may be coupled into the waveguide by an input grating 3212 and by a first output grating 3214 at an output angle equal to the input angle (e.g. It can be coupled out of the waveguide at any desired angle, such as approximately 90° in the illustrated example). The input grating 3212 and the first output grating 3214 may have matching grating vectors (eg, at least in the xy plane), thus compensating for dispersion caused by each other and keeping the output angle equal to the input angle. can.

The FOV associated with the second output grating 3216 was associated with the first output grating 3214 due to, for example, the non-zero width of each grating's diffraction efficiency curve as shown in FIGS. It may overlap at least partially with the first FOV. Thus, display light from the first field of view and coupled into the waveguide by the input grating 3212 is at least partially coupled out of the waveguide at undesired angles by the second output grating 3216. obtain. Due to the grating vector mismatch between the input grating 3212 and the second output grating 3216, the input angle (e.g., about 90° in the example) and from the waveguide within the first FOV and by the second output grating 3216 The output angle of the display light that is coupled out can vary, as shown in FIG. 32A. Therefore, undesirable ghost images may be generated.

FIG. 32B illustrates the relationship between the grating period of a volume Bragg grating and the corresponding fields of view for incident light of different colors. As illustrated, the same VBG (eg, the VBG represented by line 3230) diffracts red light at a first wavelength from the negative field of view (as indicated by the intersection of line 3230 and curve 3240). can. The same VBG may also diffract red light at different (eg, second) wavelengths from different negative fields of view (as indicated by the intersection of line 3230 and curve 3242). Red light at the first and second wavelengths may be emitted by the same light source (eg, a red LED) that emits light in a narrow spectral range. Similarly, the same VBG shows green light at a third wavelength from a positive field of view (as indicated by the intersection of line 3230 and curve 3250) and a different positive field of view (as indicated by the intersection of line 3230 and curve 3252). can diffract green light at different (eg, fourth) wavelengths from Green light at the third and fourth wavelengths can be emitted by the same light source (eg, a green LED) that emits light in a narrow spectral range. The same VBG is blue light at a fifth wavelength from a positive field of view (as indicated by the intersection of line 3230 and curve 3260) and a different positive field of view (as indicated by the intersection of line 3230 and curve 3262). ) at a different (eg, sixth) wavelength. Blue light at the fifth and sixth wavelengths can be emitted by the same light source (eg, a blue LED) that emits light in a narrow spectral range.

In some cases, ghost effects can be caused by unwanted diffraction of display light for a first field by gratings for different fields. For example, ghost images can occur if the display light for the left half of the FOV is diffracted by the top grating for the right half of the FOV, or if the display light for the right half of the FOV is diffracted by the top grating for the left half of the FOV. It can be present when diffracted by a grating. In some embodiments, two or more top gratings may be offset from each other and may not overlap to reduce ghosting effects. In some embodiments, the two or more upper gratings may be designed so that unwanted diffraction of display light by the gratings cannot reach the eyebox and thus be observed by the user.

As explained above, transmission and reflection gratings can have different performance characteristics such as diffraction efficiency, diffraction efficiency saturation, dispersion, FWHM angular range, and the like. For example, a transmission grating may have a wider Bragg peak linewidth than a reflection grating. In addition, the Bragg peak linewidth for transmitted or reflected VBG can vary with the corresponding field of view.

FIG. 33A illustrates linewidths of Bragg peaks of transmission and reflection volume Bragg gratings for different fields of view. Curve 3310 shows the linewidth of the Bragg peak of transmitted VBG for different fields of view. Curve 3310 shows that the linewidth of the Bragg peak of transmitted VBG can increase significantly with a corresponding increase in field of view. Curve 3320 illustrates the linewidth of the Bragg peak of the reflected VBG for different fields of view. Curve 3320 shows that the linewidth of the reflected VBG Bragg peak can increase only slightly with a corresponding increase in field.

FIG. 33B illustrates examples of Bragg peaks 3330 of a transmission volume Bragg grating for different fields of view. As shown, the linewidth of the transmission VBG for the larger field of view can be much wider than the linewidth of the transmission VBG for the smaller field of view, thus covering a larger FOV range.

FIG. 33C illustrates examples of Bragg peaks 3340 of a reflective volume Bragg grating for different fields of view. As shown, the linewidth of the reflected VBG for the larger field of view can be about the same as the linewidth of the reflected VBG for the smaller field of view.

FIG. 34A illustrates the tradeoff between crosstalk and efficiency in an example of a multiplexed volume Bragg grating containing multiple VBGs. In the example shown in FIG. 34A, the VBGs are sparsely multiplexed to avoid Bragg peak overlap and hence crosstalk between VBGs for blue light from large positive fields, as shown by curve 3410. can be As explained above, the VBG can also diffract other colors of light from other fields of view. Thus, a grating for diffracting blue light from positive fields can also diffract red light from negative fields. However, as explained above with respect to FIGS. 33A-33B , because the gratings are sparsely multiplexed and the linewidth of the Bragg peak of the transmission grating is narrower at negative fields, Red light may not be diffracted by the grating as indicated by the gaps between peaks in curve 3420, thus reducing the efficiency for red light in certain negative fields.

FIG. 34B illustrates the tradeoff between crosstalk and efficiency in an example of a multiplexed volume Bragg grating containing multiple VBGs. In the illustrated example, the VBG can be densely multiplexed to increase negative field coverage for red light as shown by curve 3440 . A densely multiplexed VBG can also diffract blue light from the positive field. Because the VBGs are densely multiplexed and the linewidths of the transmission grating Bragg peaks are broader in the positive field, the blue light Bragg peaks in the positive field overlap and have a large positive peak, as shown by curve 3430. can cause crosstalk between VBGs for blue light from the field of view.

Therefore, it can be difficult to minimize crosstalk and maximize efficiency in transmission gratings. In many cases, the maximum achievable efficiency of a transmissive VBG-based waveguide display can be limited by the maximum allowable crosstalk.

FIG. 35A illustrates the relationship between minimum diffraction efficiency and total refractive index modulation and corresponding crosstalk in a multiplexed transmission volume Bragg grating. The horizontal axis of FIG. 35A corresponds to the desired minimum efficiency. Data point 3520 indicates the minimum refractive index modulation to achieve the corresponding minimum desired diffraction efficiency. Data points 3510 show the maximum crosstalk value associated with the corresponding minimum refractive index modulation to achieve the corresponding minimum desired efficiency.

In the example shown in FIG. 35A, the desired crosstalk may be, for example, less than 0.06 (so that the checkerboard contrast may be approximately 30), as indicated by dashed line 3530. FIG. Each waveguide plate may have two polymer layers attached. The maximum refractive index modulation in each polymer layer may be, for example, about 0.05, such that the total refractive index modulation may be about 0.1 as indicated by dashed line 3540 . As indicated by data points 3542, when the total refractive index modulation of the two polymer layers is 0.1 to achieve the desired efficiency, the crosstalk is less than the maximum allowable crosstalk indicated by dashed line 3530. could be much higher. As shown by data point 3532, to achieve crosstalk of less than 0.06, the maximum refractive index modulation of the polymer layer may not be fully utilized and the minimum efficiency may be relatively low. In the example illustrated by data point 3532 in FIG. 35A, only about 20% of the total refractive index modulation of the two polymer layers can be utilized to achieve crosstalk performance. Hence, the efficiency of transmissive VBG-based waveguide displays may be limited by the maximum allowable crosstalk.

FIG. 35B illustrates the relationship between minimum diffraction efficiency and total refractive index modulation and corresponding crosstalk in a multiplexed reflective volume Bragg grating. The horizontal axis corresponds to the desired minimum efficiency. Data point 3570 shows the refractive index modulation to achieve the corresponding desired minimum efficiency. Data point 3560 indicates the maximum crosstalk value associated with the corresponding refractive index modulation to achieve the corresponding minimum desired efficiency.

In the example shown in FIG. 35B, each waveguide plate may have two polymer layers attached. The maximum refractive index modulation in each polymer layer may be, for example, about 0.05, such that the total refractive index modulation may be, for example, about 0.1, as indicated by dashed line 3580 . When the maximum refractive index modulation (eg, 0.1) of the polymer layer is fully utilized, as indicated by point 3582 in FIG. (eg, about 0.06), the efficiency can be relatively high. Therefore, in reflective VBG-based waveguide displays, the diffraction efficiency can be limited by the maximum refractive index modulation of the polymer layers. In various embodiments, the transmission and reflection gratings may be selected based on design considerations such as form factor, efficiency, image quality, and the like.

Transmissive VBG and reflected VBG characteristics and desired characteristics of waveguide displays such as efficiency, field of view, resolution, contrast, crosstalk, ghost images, rainbow effect, physical dimensions, and the like. Or a reflective VBG can be chosen to implement a waveguide display. For example, as described above with respect to Figures 27B and 29A-29D, in reflective gratings the diffraction efficiency can saturate when the refractive index modulation exceeds a threshold value. The FWHM angular range or FWHM wavelength range can widen as the refractive index modulation continues to increase. Such properties of reflected VBG can be exploited in some waveguide systems.

For example, in the waveguide display example, the light source in the project may emit light in a wavelength bandwidth of about 10 nm to about 30 nm. For an unsaturated reflective VBG with a thickness of about 50 μm, the FWHM wavelength range may be about 1 nm. Therefore, multiple VBGs may be required to diffract the emitted light in the wavelength bandwidth of the source. The FWHM wavelength range of a saturated reflective VBG with a thickness of about 50 μm can be much wider than 1 nm, so less reflective VBG diffracts emitted light that is in the wavelength bandwidth of the source. may be required for

FIG. 36 illustrates an example waveguide display 3600 including spatially multiplexed reflective volume Bragg gratings with different refractive index modulations, according to certain embodiments. The reflective VBG shown in FIG. 36 can be used for one-dimensional pupil expansion and dispersion compensation. Note that the reflected VBG shown in FIG. 36 is for illustrative purposes only. In some embodiments, an additional reflective or transmissive VBG grating 3615 can be used to expand the pupil in another dimension to achieve pupil expansion in two dimensions as described above. For example, VBG grating 3615 may include another set of reflective VBGs that may be used for pupil expansion and dispersion compensation in a second dimension substantially perpendicular to the first dimension as described above.

In the example shown in FIG. 36, waveguide display 3600 may include first reflective grating 3610 and second reflective grating 3620 . The first reflective grating 3610 and the second reflective grating 3620 can have matching grating vectors, such as the same grating vectors in the xy plane and the same and/or opposite grating vectors in the z direction. For example, first reflective grating 3610 and second reflective grating 3620 may have some of the same grating parameters, such as grating period, tilt angle, and thickness, and the like. First reflective grating 3610 and second reflective grating 3620 may compensate for dispersion caused by each other as described above.

In some embodiments, first reflective grating 3610 may be an example of the input gratings described above, such as input gratings 1922, 2222, 2252, 2330, 2332, and the like. Second reflective grating 3620 may be an example of an output or lower grating, such as second grating 1940, lower grating 2240, lower gratings 2350 and 2352, and the like. A first reflective grating 3610 and a second reflective grating 3620 may be used to couple display light into and out of the waveguide, respectively.

In some embodiments, first reflective grating 3610 comprises first portion 1932 of first grating 1930 , first portion 2232 of first upper grating 2230 , first portion 2232 of second upper grating 2260 . It can be an example of portion 2262, the first portion of upper grid 2340, the first portion of upper grid 2342, and the like. Second reflective grating 3620 may be an example of other portions of first grating 1930, first upper grating 2230, second upper grating 2260, upper grating 2340, upper grating 2342, and the like.

In waveguide display 3600, first reflective grating 3610 and second reflective grating 3620 may have different refractive index modulations. For example, the first reflective grating 3610 may be strongly saturated, so the diffraction efficiency of the first reflective grating 3610 may be approximately indicated by the diagram 3612, and the FWHM wavelength range (and/or FWHM angle range) may be large It may be wide to cover a wavelength range (and/or a large FOV range). Thus, the first reflective grating 3610 can diffract display light in a large wavelength range (and/or a large FOV range).

The second reflective grating 3620 may include multiple areas 3622, 3624, 3626, and the like. Display light diffracted by the first reflective grating 3610 (e.g., coupled into the waveguide or deflected in different directions) may propagate with the waveguide through total internal reflection, either directly or indirectly. Each of the multiple areas of the second reflective grating 3620 can be reached in a targeted manner (eg, through the grating 3615). The multiple sections of the second reflective grating 3620 may each couple a portion of the display light out of the waveguide, for example, or towards the output (or lower) grating. Each of the plurality of zones 3622, 3624, 3626, and the like may have different respective refractive index modulations and thus may be saturated at different respective levels, resulting in different respective FWHM wavelength ranges (and/or FWHM angles). range). For example, the first region 3622 may have a refractive index modulation below, at, or just above the saturation level, and thus may have the diffraction efficiency curve shown by diagram 3632 . A second zone 3624 may have a higher refractive index modulation and thus a wider FWHM wavelength range (and/or FWHM angle range) as shown by diagram 3634 . A third zone 3626 may have an even higher refractive index modulation and thus a much wider FWHM wavelength range (and/or FWHM angle range) as shown by diagram 3636 . In some embodiments, the second reflective grating 3620 can include multiple (eg, four or more) sections that can have different refractive index modulations and different FWHM wavelength ranges (and/or FWHM angle ranges). .

In some embodiments, the first area 3622 of the second reflective grating 3620 directs display light in the first wavelength (and/or FOV) range to a high efficiency (eg, 100° as shown by graphic 3632). %) from the waveguide to replicate a pupil for light in the first wavelength (and/or FOV) range. A second section 3624 of the second reflective grating 3620 may couple display light in a second wavelength (and/or FOV) range out of the waveguide with high efficiency as shown by graphic 3634 . The second wavelength (and/or FOV) range may include the first wavelength (and/or FOV) range and may be wider than the first wavelength (and/or FOV) range. Since most or all of the light at the first wavelength (and/or FOV range) may have been diffracted by the first area 3622, the second area 3624 is at the second wavelength (and/or FOV) range can only be diffracted and not diffracted by the first area 3622 as indicated by area 3644 in figure 3634 to replicate another pupil. Similarly, a third section 3626 of the second reflective grating 3620 couples display light in a third wavelength (and/or FOV) range out of the waveguide with high efficiency as shown by graphic 3636. obtain. The third wavelength (and/or FOV) range may include the second wavelength (and/or FOV) range and may be wider than the second wavelength (and/or FOV) range. Since most or all of the light in the second wavelength (and/or FOV) range may have been diffracted by the first area 3622 and the second area 3624, the third area 3626 is the third , and is diffracted by first area 3622 and second area 3624 as shown in diagram 3636 to replicate a third pupil. do not have.

In some embodiments, the first reflective grating 3610 and the second reflective grating 3620 may each be a grating within a respective multiplexed grating including multiple saturated reflective VBGs. Each saturated reflection VBG within the multiplexed grating is red, green, and/or from a different respective wavelength and/or FOV range, eg, as described above with respect to FIGS. 26A, 26B, and 32B. or can diffract blue light. Multiple saturated reflected VBGs are thus emitted by a light source (e.g., red, green, and blue LEDs), e.g., as described above with respect to Figures 19B, 22B, 23B, 25, and 33C. may provide a full FOV for red, green, and blue light of the displayed image.

In some embodiments, since the diffraction efficiency of the transmission grating is polarization sensitive and the incoming display light may be unpolarized, some components of the display light may not be diffracted by the grating; Hence, the efficiency of waveguide displays can be reduced. To improve the efficiency of unpolarized light or light in a particular polarization state, a polarization converter and two spatially multiplexed gratings are used to couple the display light into a waveguide or can be used to couple out from.

FIG. 37 illustrates an example waveguide display 3700 including two multiplexed volume Bragg gratings 3710 and 3740 and a polarization converter 3730 between the two multiplexed volume Bragg gratings 3710 and 3740, in accordance with certain embodiments. is. In some embodiments, since the diffraction efficiency of the transmission grating is polarization sensitive and the incoming display light may be unpolarized, some components of the display light may not be diffracted by the grating; Hence, the efficiency of waveguide displays can be reduced. To improve the efficiency of unpolarized light or light in a particular polarization state, a polarization converter and two spatially multiplexed gratings are used to couple the display light into a waveguide or can be used to couple out from. A first VBG 3710 can be formed on the substrate 3720 or on the surface of the polarization converter 3730 . A second VBG 3740 may be formed on substrate 3750 or on another surface of polarization converter 3730 .

Unpolarized light 3702 may include s-polarized light and p-polarized light. The first VBG 3710 may diffract most of the s-polarized light and some of the p-polarized light, as shown by diffracted light 3704 . Diffracted light 3704 is partially converted by polarization converter 3730 and may pass through second VBG 3740 without being diffracted by second VBG 3740, as shown by transmitted light 3706, because the Bragg condition is not satisfied. . The portion of the p-polarized light 3708 that is not diffracted by the first VBG 3710 may pass through a polarization converter 3730 and be converted to s-polarized light and diffracted by the second VBG 3740 such that the diffracted light 3712 is , may have the same direction of propagation as the transmitted light 3706 . In this manner, unpolarized light 3702 can be diffracted by waveguide display 3700 more efficiently.

External light (eg, from an external light source such as a lamp or the sun) may be reflected at the surface of the grating coupler and return to the grating coupler, and the reflected light may be diffracted by the grating coupler to produce a rainbow image. In some waveguide displays, ambient light with large angles of incidence outside the see-through field of view of the waveguide display can also be diffracted by the grating coupler to produce a rainbow image. According to some embodiments, additional structures such as reflective coating layers (e.g., for light from a large see-through FOV) and/or anti-reflection coating layers (e.g., for light from a small see-through FOV) are It can be used in waveguide displays to reduce optical artifacts such as the rainbow effect. For example, an angle-selective transmissive layer can be placed in front of (or behind) the waveguide and the grating coupler of the waveguide display to reduce artifacts caused by external light sources. The angle-selective transmissive layer allows ambient light within the see-through field of view of the near-eye display to pass through and reach the user's eye with little loss, while reducing the see-through field of view to half that of the waveguide display. can be configured to reflect, diffract, or absorb ambient light having angles of incidence greater than . Angularly selective transmissive layers include, for example, one or more dielectric layers, diffractive elements such as gratings (eg, metagratings), nanostructures (eg, nanowires, nanopillars, nanoprisms, nanopyramids), and the like. It can contain a coating that can contain things.

FIG. 38 illustrates an example waveguide display 3800 including an antireflective layer 3850 and an angle selective transmissive layer 3840, according to certain embodiments. Waveguide display 3800 may include waveguide 3810 and grating coupler 3820 on the underside of waveguide 3810 . Grating coupler 3820 may be similar to the grating couplers described above. External light 3830 incident on waveguide 3810 may be refracted into waveguide 3810 as external light 3832 and then diffracted by grating coupler 3820 . The diffracted light may include the 0th diffraction order 3834 (eg, refractive diffraction) and the −1st diffraction order (not shown). The height, period, and/or tilt angle of grating coupler 3820 can be configured such that −1 order diffraction can be reduced or minimized for extraneous light.

Waveguide display 3800 may include antireflection layer 3850 on bottom surface 3822 of grating coupler 3820 . Antireflective layer 3850 may include, for example, one or more dielectric thin film layers or other antireflective layers coated on lower surface 3822 and may be used to reduce reflection of external light at lower surface 3822 . Therefore, very little external light can be reflected back to the grating coupler 3820 at the bottom surface 3822 of the grating coupler 3820, and thus can otherwise form due to diffraction of external light reflected at the bottom surface 3822 by the grating coupler 3820. Rainbow ghosting can be reduced or minimized. Some portion of the display light may be diffracted by grating coupler 3820 and coupled out of waveguide 3810 toward the user's eye (eg, due to −1st order diffraction). Antireflection layer 3850 may also help reduce reflection of the portion of display light that is coupled out of waveguide 3810 by grating coupler 3820 .

An angle-selective transmissive layer 3840 may be coated on top of waveguide 3810 or grating coupler 3820 . The angle-selective transmissive layer 3840 can have high reflectivity, high diffraction efficiency, or high absorption for incident light with angles of incidence greater than a certain threshold, and for incident angles below the threshold. can have low loss for incident light with The threshold can be determined based on the see-through field of view of waveguide display 3800 . For example, incident light 3860 having an angle of incidence greater than the see-through field of view may be largely reflected, diffracted, or absorbed by the angle-selective transmissive layer 3840 and thus may not reach waveguide 3810 . External light 3830 having an angle of incidence within the see-through field of view can mostly pass through the angle-selective transmission layer and waveguide 3810 and be refracted or diffracted by grating coupler 3820 .

The angle-selective transmissive layer 3840 described above can be implemented in various ways. In some embodiments, the angularly selective transmissive layer can include one or more dielectric layers (or air gaps). Each dielectric layer may have a respective refractive index, and adjacent dielectric layers may have different refractive indices. In some embodiments, an angle-selective transmissive layer can include, for example, micromirrors or prisms, gratings, metagratings, nanowires, nanopillars, or other micro- or nanostructures. In some examples, the angularly selective transmissive layer can include a grating with a small grating period (eg, a surface relief grating or a holographic grating) formed on the substrate. The grating may only diffract light having large angles of incidence (eg, about 75° to about 90°), and the diffracted light may propagate in directions such that the diffracted light cannot reach the eyebox. The grating period can be, for example, less than 280 nm (eg, about 200 nm) so that the angle-selective transmissive layer cannot affect light within the see-through field of view. In some examples, the angle-selective transmissive layer can include microscale or nanoscale anisotropic structures that can reflect, diffract, or absorb incident light having large angles of incidence. Anisotropic structures can include, for example, large aspect ratio nanoparticles aligned and immersed in transparent media, nanowire arrays, certain liquid crystal materials, and the like.

Embodiments of the invention may be used to implement components of an artificial reality system, or may be implemented in conjunction with an artificial reality system. Artificial reality may include, for example, virtual reality (VR), augmented reality (AR), mixed reality (MR), hybrid reality, or any combination and/or derivative thereof, in some manner prior to presentation to a user. It is a form of reality that is being adjusted. Artificial reality content may include fully generated content or generated content combined with captured (eg, real-world) content. Artificial reality content may include video, audio, haptic feedback, or some combination thereof, any of which may be presented in a single channel or multiple channels (providing a three-dimensional effect to the viewer). stereo moving images, etc.). Additionally, in some embodiments, artificial reality is also used, for example, to create content in artificial reality and/or otherwise used in artificial reality (e.g., to conduct activities in artificial reality). ), applications, products, accessories, services, or some combination thereof. An artificial reality system that provides artificial reality content provides artificial reality content to a head-mounted display (HMD) connected to a host computer system, a standalone HMD, a mobile device or computing system, or one or more viewers. It can be implemented on a variety of platforms, including any other hardware platform capable.

FIG. 39 is a simplified block diagram of an example electronic system 3900 for an example near-eye display (eg, HMD device) for implementing some of the examples disclosed herein. The electronic system 3900 can be used as the HMD device or other near-eye display electronic system described above. In this example, electronic system 3900 may include one or more processors 3910 and memory 3920 . Processor 3910 may be configured to execute instructions to perform operations on a number of components, and may be, for example, a general purpose processor or a microprocessor suitable for implementation within a portable electronic device. Processor 3910 may be communicatively coupled to multiple components within electronic system 3900 . To achieve this communicative coupling, processor 3910 may communicate with other illustrated components over bus 3940 . Bus 3940 may be any subsystem adapted to transfer data within electronic system 3900 . Bus 3940 may include multiple computer buses and additional circuitry to transfer data.

Memory 3920 may be coupled to processor 3910 . In some embodiments, memory 3920 may provide both short-term and long-term memory and may be divided into several units. Memory 3920 may be volatile, such as static random access memory (SRAM) and/or dynamic random access memory (DRAM), and/or non-volatile, such as read only memory (ROM), flash memory, and the like. good too. Additionally, memory 3920 may include removable storage devices such as Secure Digital (SD) cards. Memory 3920 may provide storage of computer readable instructions, data structures, program modules and other data for electronic system 3900 . In some embodiments, memory 3920 may be distributed across different hardware modules. A set of instructions and/or code may be stored in memory 3920 . The instructions may be in the form of executable code that may be executable by electronic system 3900 and/or compiled and/or installed on electronic system 3900 (e.g., various commonly available compilers, It can take the form of source and/or installable code, which can take the form of executable code when installed (either using an installation program, compression/decompression utility, etc.).

In some embodiments, memory 3920 may store multiple application modules 3922-3924, which may include any number of applications. Examples of applications may include gaming applications, conferencing applications, video playback applications, or other suitable applications. Applications may include depth sensing or eye tracking functionality. Application modules 3922 - 3924 may contain specific instructions to be executed by processor 3910 . In some embodiments, certain applications or portions of application modules 3922 - 3924 may be executable by other hardware modules 3980 . In certain embodiments, memory 3920 may additionally include secure memory that may include additional security controls to prevent copying or other unauthorized access to secure information.

In some embodiments, memory 3920 may include an operating system 3925 loaded thereon. Operating system 3925 initiates execution of instructions provided by application modules 3922-3924 and/or other hardware modules using wireless communication subsystem 3930, which may include one or more wireless transceivers. 3980 as well as interfaces. Operating system 3925 may be adapted to perform other operations across components of electronic system 3900, including threading, resource management, data storage control, and other similar functionality.

Wireless communication subsystem 3930 includes, for example, infrared communication devices, wireless communication devices and/or chipsets (Bluetooth devices, IEEE 802.11 devices, Wi-Fi devices, WiMax devices, cellular communication facilities, etc.), and /or may include a similar communication interface. Electronic system 3900 may include one or more antennas 3934 for wireless communication, either as part of wireless communication subsystem 3930 or as separate components coupled to any portion of the system. Depending on the desired functionality, the wireless communication subsystem 3930 communicates with different data networks and/or network types such as wireless wide area networks (WWAN), wireless local area networks (WLAN), or wireless personal area networks (WPAN). Separate transceivers may be included for communicating with the base transceiver base station and other wireless devices and access points. A WWAN may be, for example, a WiMax (IEEE 802.16) network. A WLAN may be, for example, an IEEE 802.11x network. A WPAN may be, for example, a Bluetooth network, IEEE 802.15x, or some other type of network. The techniques described herein may also be used for any combination of WWAN, WLAN, and/or WPAN. Wireless communication subsystem 3930 may allow data to be exchanged with networks, other computer systems, and/or any other device described herein. Wireless communication subsystem 3930 includes means for transmitting or receiving data such as HMD device identifiers, location data, geographic maps, heat maps, photos, or videos using antenna 3934 and wireless link 3932. obtain. Wireless communication subsystem 3930, processor 3910, and memory 3920 together may comprise at least part of one or more of the means for performing certain functions disclosed herein.

Embodiments of electronic system 3900 may also include one or more sensors 3990 . Sensors 3990 may be, for example, image sensors, accelerometers, pressure sensors, temperature sensors, proximity sensors, magnetometers, gyroscopes, inertial sensors (eg, accelerometer and gyroscope combined modules), ambient light sensors, or depth sensors. It may include any other similar module operable to provide sensor output and/or receive sensor input, such as sensors or position sensors. For example, in some implementations, sensors 3990 may include one or more inertial measurement units (IMUs) and/or one or more position sensors. The IMU may generate calibration data indicating an estimated position of the HMD device relative to an initial position of the HMD device based on measurement signals received from one or more of the position sensors. A position sensor may generate one or more measurement signals in response to movement of the HMD device. Examples of position sensors include, but are not limited to, one or more accelerometers, one or more gyroscopes, one or more magnetometers, another suitable type of sensor that detects motion, It may include sensors of the type used for IMU error correction, or some combination thereof. The position sensor may be located external to the IMU, internal to the IMU, or any combination thereof. At least some sensors may use structured light patterns for sensing.

Electronic system 3900 may include display module 3960 . Display module 3960 may be a near-eye display and may graphically present information such as images, movies, and various instructions from electronic system 3900 to a user. Such information may include one or more application modules 3922-3924, virtual reality engine 3926, one or more other hardware modules 3980, combinations thereof, or graphical content for a user (eg, operating system 3925) from any other suitable means for decomposing. The display module 3960 may use liquid crystal display (LCD) technology, light emitting diode (LED) technology (including, for example, OLED, ILED, μLED, AMOLED, TOLED, etc.), light emitting polymer display (LPD) technology, or some other display technology. can be used.

Electronic system 3900 may include user input/output module 3970 . User input/output module 3970 may allow a user to send action requests to electronic system 3900 . An action request may be a request to perform a particular action. For example, an action request may be to start or end an application, or to perform a particular action within the application. User input/output module 3970 may include one or more input devices. Exemplary input devices include touch screens, touch pads, microphones, buttons, dials, switches, keyboards, mice, game controllers, or any device for receiving action requests and communicating received action requests to electronic system 3900. Other suitable devices may be included. In some embodiments, user input/output module 3970 may provide tactile feedback to the user according to instructions received from electronic system 3900 . For example, haptic feedback may be provided when an action request is received or performed.

The electronic system 3900 may include a camera 3950 that may be used to take pictures or videos of the user, eg, for tracking the position of the user's eyes. Camera 3950 may also be used to take pictures or videos of the environment for VR, AR, or MR applications, for example. Camera 3950 may include, for example, a complementary metal oxide semiconductor (CMOS) image sensor having millions or tens of millions of pixels. In some implementations, camera 3950 may include two or more cameras that may be used to capture 3D images.

In some embodiments, electronic system 3900 may include multiple other hardware modules 3980 . Each of the other hardware modules 3980 may be physical modules within electronic system 3900 . Each of the other hardware modules 3980 may be permanently configured as a structure, while some of the other hardware modules 3980 may be temporarily configured to perform specific functions or temporarily can be launched at Examples of other hardware modules 3980 are, for example, audio output and/or input modules (eg, microphone or speaker), Near Field Communication (NFC) modules, rechargeable batteries, battery management systems, wired/wireless battery charging systems. and so on. In some embodiments, one or more functions of other hardware modules 3980 may be implemented in software.

In some embodiments, memory 3920 of electronic system 3900 may also store virtual reality engine 3926 . A virtual reality engine 3926 may run an application within the electronic system 3900 and may receive HMD device position information, acceleration information, velocity information, predicted future position, or some combination thereof from various sensors. In some embodiments, information received by virtual reality engine 3926 may be used to generate signals (eg, display instructions) to display module 3960 . For example, if the received information indicates that the user looked left, the virtual reality engine 3926 may generate content for the HMD device that reverses the user's movements in the virtual environment. Additionally, the virtual reality engine 3926 may perform actions within the application in response to action requests received from the user input/output module 3970 and provide feedback to the user. The feedback provided can be visual, audible, or tactile feedback. In some implementations, processor 3910 may include one or more GPUs that may run virtual reality engine 3926 .

In various implementations, the hardware and modules described above can be implemented in a single device or multiple devices that can communicate with each other using wired or wireless connections. For example, in some implementations, some components or modules such as the GPU, virtual reality engine 3926, and applications (eg, tracking applications) may be implemented in a console separate from the head-mounted display device. In some implementations, one console may connect to or support more than one HMD.

Different and/or additional components may be included in electronic system 3900 in alternative configurations. Similarly, the functionality of one or more of the components may be distributed among the components in manners other than those described above. For example, in some embodiments, electronic system 3900 may be modified to include other system environments such as AR system environments and/or MR environments.

The methods, systems, and devices discussed above are examples. Various embodiments may omit, substitute, or add various procedures or components as appropriate. For example, in alternative arrangements, the methods described may be performed in a different order than described, and/or various stages may be added, omitted, and/or combined. Also, features described with respect to certain embodiments may be combined in various other embodiments. Different aspects and elements of the embodiments can be combined in a similar manner. Also, technology evolves, and thus many of the elements are examples that do not limit the scope of the invention to those particular examples.

Specific details are given in the description to provide a thorough understanding of the embodiments. However, embodiments may be practiced without these specific details. For example, well-known circuits, processes, systems, structures, and techniques have been shown without unnecessary detail in order to avoid obscuring the embodiments. This description provides exemplary embodiments only and is not intended to limit the scope, applicability, or configuration of the invention. Rather, the preceding description of the embodiments will provide those skilled in the art with an enabling description for implementing various embodiments. Various changes may be made in the function and arrangement of elements without departing from the scope of the invention as defined in the appended claims.

Also, some embodiments have been described as processes depicted as flow diagrams or block diagrams. Although each may describe the operations as a sequential process, many of the operations can be performed in parallel or concurrently. Additionally, the order of operations may be rearranged. A process may have additional steps not included in the figure. Moreover, embodiments of the method may be implemented by hardware, software, firmware, middleware, microcode, hardware description languages, or any combination thereof. When implemented in software, firmware, middleware, or microcode, the program code or code segments for performing the relevant tasks may be stored on a computer-readable medium such as a storage medium. A processor may perform related tasks.

It is clear to those skilled in the art that substantial variations can be made according to specific requirements. For example, customized or special-purpose hardware may also be used, and/or particular elements may be implemented in hardware, software (including portable software such as applets), or both. Additionally, connections to other computing devices, such as network input/output devices, may be employed.

With reference to the accompanying figures, components that may include memory may include non-transitory machine-readable media. The terms "machine-readable medium" and "computer-readable medium" can refer to any storage medium that participates in providing data that causes a machine to operate in a specified manner. In the embodiments provided hereinabove, various machine-readable media may be involved in providing instructions/code to a processing unit and/or other device for execution. Additionally or alternatively, a machine-readable medium may be used to store and/or retain such instructions/code. In many implementations, a computer-readable medium is a physical and/or tangible storage medium. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Common forms of computer-readable media include, for example, magnetic and/or optical media such as compact discs (CDs) or digital versatile discs (DVDs), punch cards, paper tape, any other physical media having a pattern of holes. , RAM, programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), FLASH-EPROM, any other memory chip or cartridge, carrier wave as described hereinafter, or computer may include any other medium on which instructions and/or code can be read. A computer program product may represent procedures, functions, subprograms, programs, routines, applications (Apps), subroutines, modules, software packages, classes, or any combination of instructions, data structures, or program statements, code and /or may include machine-executable instructions.

Those of skill in the art should understand that the information and signals used to communicate the messages described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, codes, and chips that may be referred to throughout the above description may refer to voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, light fields or particles, or any of these. It can be represented by a combination.

The terms "and" and "or", as used herein, have various meanings that are also expected to depend, at least in part, on the context in which such terms are used. can contain. Typically, when used to associate lists such as A, B, or C, "or" is used in an inclusive sense, A, B, and C, and is used in an exclusive sense. is intended to mean A, B, or C. In addition, the term “one or more,” as used herein, may be used to describe any feature, structure, or property in the singular or to describe any feature, structure, or property. Can be used to describe any combination. Note, however, that this is merely an illustrative example and claimed subject matter is not limited to this example. Further, the term "at least one" when used to associate lists such as A, B, or C means A, AB, AC, BC, AA, ABC, AAB, AABBCCC, etc., A, B, and/or may be taken to mean any combination of C.

Furthermore, although certain embodiments have been described using a particular combination of hardware and software, it should be appreciated that other combinations of hardware and software are possible. Certain embodiments may be implemented using hardware only, software only, or a combination thereof. In one example, software is a computer program product comprising computer program code or instructions executable by one or more processors to perform any or all of the steps, acts, or processes described in this disclosure. can be implemented with The various processes described herein may be performed on the same processor or different processors in any combination.

When a device, system, component, or module is described as being configured to perform a particular operation or function, such configuration refers, for example, to designing an electronic circuit to perform the operation. by programming a programmable electronic circuit (such as a microprocessor) to perform the operations, such as by executing computer instructions or code, or by executing code or instructions stored in a non-transitory memory medium It may be accomplished by a processor or core programmed to do so, or any combination thereof. Processes may communicate using a variety of techniques including, but not limited to, conventional techniques for interprocess communication, and different process pairs may use different techniques, or the same process pair may communicate using , may use different techniques at different times.

The invention is defined in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. However, it will be apparent that additions, subtractions, deletions, and other modifications and changes may be made thereto without departing from the scope as set forth in the claims. Thus, although specific embodiments have been described, they are not intended to be limiting. Various modifications and equivalents are within the scope of the following claims.

Claims (15)

a substrate;
a first reflective volume Bragg grating (VBG) on the substrate and characterized by a first refractive index modulation;
a second reflective VBG on said substrate and comprising first and second regions, said waveguide display comprising:
The first reflective VBG is configured to diffract display light in a first wavelength range such that the display light in the first wavelength range undergoes total internal reflection within the substrate. through to the first region and the second region of the second reflected VBG;
The first region of the second reflective VBG is characterized by a second refractive index modulation lower than the first refractive index modulation and for a second wavelength range within the first wavelength range. configured to diffract some display light,
The second region of the second reflective VBG is characterized by a third refractive index modulation that is greater than the second refractive index modulation, includes the second wavelength range and is greater than the second refractive index modulation. A waveguide display configured to diffract display light in three wavelength ranges. The first region and the second region of the second reflected VBG are arranged such that the display light in the first wavelength range reaches the second region after reaching the first region. 2. The waveguide display of claim 1, wherein the waveguide display is arranged in a . the third refractive index modulation is less than or equal to the first refractive index modulation;
3. A waveguide display according to claim 1 or 2, wherein the first wavelength range is the same as or includes the third wavelength range. 4. A waveguide display according to any one of claims 1 to 3, wherein said first reflected VBG and said second reflected VBG have the same grating vector in a plane perpendicular to the surface normal direction of said substrate. said second reflective VBG further comprising a third region between said first region and said second region, said third region being greater than said second refractive index modulation, display light in a fourth wavelength range characterized by a fourth refractive index modulation lower than the third refractive index modulation, and comprising the second wavelength range and within the third wavelength range; 5. A waveguide display according to any one of claims 1 to 4, arranged to be diffractive. a third reflective VBG multiplexed with the first reflective VBG and characterized by a fourth refractive index modulation;
a fourth reflected VBG multiplexed with the second reflected VBG in the first and second regions;
The third reflective VBG is configured to diffract display light in a fourth wavelength range such that the display light in the fourth wavelength range undergoes total internal reflection within the substrate. through to the first region and the second region of the fourth reflected VBG;
The first region of the fourth reflective VBG is characterized by a fifth refractive index modulation lower than the fourth refractive index modulation and for a fifth wavelength range within the fourth wavelength range. configured to diffract some display light,
The second region of the fourth reflective VBG is characterized by a sixth refractive index modulation that is greater than the fifth refractive index modulation, includes the fifth wavelength range and a greater than the fifth refractive index modulation. 6. A waveguide display according to any one of the preceding claims, arranged to diffract display light in six wavelength ranges. The first reflected VBG is
Diffracts display light in said first wavelength range and a first field of view (FOV) range, and diffracts display light in a fourth wavelength range and a second FOV range different from said first FOV range. be configured to
7. Any one of claims 1 to 6, wherein the substrate is one or more of transparent to visible light, and the second reflective VBG is transparent to visible light from the surrounding environment. waveguide display. said first reflective VBG configured to couple said display light in said first wavelength range into said substrate;
8. A waveguide display as claimed in any preceding claim, wherein the second reflective VBG is configured to couple out the display light in the first wavelength range from the substrate. further comprising a third grating and a fourth grating;
the third grating is configured to diffract the display light in the first wavelength range from the first reflected VBG to the fourth grating;
the fourth grating is configured to diffract the display light in the first wavelength range in two or more regions of the fourth grating to the second reflected VBG;
9. A waveguide display according to claim 8, wherein optionally said third grating and said fourth grating have the same grating vector in a plane perpendicular to the surface normal direction of said substrate. an input coupler configured to couple the display light in the first wavelength range into the substrate;
an output coupler configured to couple out the display light diffracted by the second reflected VBG from the substrate;
10. A waveguide display according to any one of claims 1 to 9, optionally wherein said input coupler and said output coupler comprise multiplexed VBGs. a light source configured to generate the display light;
11. A waveguide display as claimed in any preceding claim, further comprising projector optics configured to collimate the display light and direct the display light to the first reflected VBG. a waveguide that transmits visible light;
a first reflective volume Bragg grating (VBG) on the waveguide and characterized by a first refractive index modulation;
a second reflective VBG on said waveguide and comprising a plurality of regions characterized by different respective refractive index modulations, said waveguide display comprising:
The first reflective VBG is configured to diffract display light in a first wavelength range and a first field of view (FOV) range such that the first wavelength range and the first FOV the display light in range propagates in the waveguide through total internal reflection to the plurality of regions of the second reflected VBG;
A waveguide display, wherein the plurality of regions of the second reflective VBG are configured to diffract the display light within different respective wavelength ranges within the first wavelength range and the first FOV range. . 13. The waveguide display of claim 12, wherein said first reflection VBG and said second reflection VBG have the same grating vector in a plane perpendicular to the plane normal direction of said waveguide. at least one of the first refractive index modulation and the different respective refractive index modulations of the plurality of regions of the second reflective VBG is greater than a minimum refractive index modulation for diffraction efficiency saturation;
The plurality of regions of the second reflected VBG is a first region of the plurality of regions in which the display light in the first wavelength range and the first FOV range has a second refractive index modulation. reaching a second region of the plurality of regions having a third refractive index modulation greater than the second refractive index modulation after reaching a
14. A waveguide display according to claim 12 or 13, which is one or more of: The first reflected VBG is configured to couple the display light in the first wavelength range and the first FOV range into the waveguide; configured to couple out the display light in the first wavelength range and the first FOV range from the waveguide, and to transmit visible light from an ambient environment;
the third grating is configured to diffract the display light in the first wavelength range and the first FOV range from the first reflective grating to the fourth grating;
The fourth grating is configured to diffract the display light in the first wavelength range and the first FOV range in two or more regions of the fourth grating to the second reflected VBG. and said third grating and said fourth grating have the same grating vector in a plane perpendicular to the plane normal direction of said waveguide. A waveguide display according to any one of Claims 1 to 3.

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